Friday, April 24, 2015

Plumbing the depths of the effective lower bound

Unfathomable Depths by Ibai Acevedo

Denmark's Nationalbank and the Swiss National Bank are the world's most interesting central banks right now. As the two of them push their deposit rates to record low levels of -0.75%, they're testing the market's limit for bearing negative nominal interest rates. The ECB takes second prize as it has been maintaining a -0.2% deposit rate since September 2014. At some point, investors will flee deposits into 0%-yielding cash. This marks the effective lower bound to rates. Has mass paper storage begun? The last time I ran through the data was in my monetary canaries post, which was inconclusive. Let's take quick glance at the updated data.

To gauge where we are relative to the effective lower bound, I'm most interested in the demand for large denomination notes, which bear the lowest costs of storage. Once a central bank reduces its deposit rate so deep into negative territory that the carrying cost of deposits exceeds the cost of storing a nation's largest value banknote, then it has hit the effective lower bound. Small denominations notes, which have higher storage costs, are not a pivotal part of the picture given the ability of note holders to freely convert low value notes into higher ones.

European Central Bank

The ECB issues the 500 note, which has the second highest purchasing power out of the world's currency notes. I've charted the quantity of 500 euro notes in circulation below, as well as the percent change in the value of all euro denominations:

After declining through 2012 and 2013, we saw a sharp rise in demand for €500 notes, particularly in December 2014 and the first few months of 2015. The red line illustrates the general demand for all denominations of euro cash. Over the last four months the seasonally-adjusted growth rate of banknotes outstanding has risen to its highest level in the last five years.

It's hard to determine how much of this increase can be attributed to the ECB's negative rate policy, initiated when Mario Draghi brought the deposit facility rate to -0.1% in June and -0.2% in September, and how much is due to the Greek fiasco. Growing fears that Greece will either leave the euro or impose capital controls have led to a steady jog out Greek banks. There are two escape routes: Greek's can convert their deposits can into German deposits or into cash.

In an interesting article, Bloomberg's Lorcan Roche Kelly backs out the Greek-specific demand for European cash. Read it for the full details, but the shorter rendition is that a line item on the Bank of Greece's balance sheet allows us to see how many banknotes Greeks are demanding in excess of the Bank of Greece's regular allocation. Kelly finds a large spike beginning in December and extending into 2015, which we can attribute to the bank jog. I've recreated the chart below:

Source: Bloomberg, data to end of March

The approximately €12 billion jump in Greek cash demand corresponds nicely with the recent €7.2 billion spike in €500 notes across the entire eurozone. The upshot is that a large chunk of the rise in 500 euro notes over the last few months is probably due to a run on Greek banks, not an escape from negative-yielding ECB deposits. Remove the run and the rise in demand for €500 notes would have been unremarkable, indicating that the eurozone is still far from hitting the effective lower bound.

Swiss National Bank

Because Swiss banknotes are not a direct escape route from the ongoing Greek bank run, SNB cash data should (in theory) provide a clearer signal of the whereabouts of the effective lower bound than ECB data. The SNB issues the world's most valuable banknote in terms of purchasing power; the 1000 franc note. Below I've plotted the yearly percent change in demand for both the 1000 note and Swiss cash-in-general to the end of February.

There's been slight pickup in the demand for Swiss cash, but nothing dramatic. Its worth pointing out that Swiss paper currency has historically played a safe haven role. Demand tends to spike during episodes of uncertainty, including the 2008 credit crisis and the 2011-12 period, when it seemed like the euro could be torn apart. This means that it is difficult to be sure how much of the recent pickup in demand for Swiss cash stems from the SNB's -0.75% deposit rate and how much is due to fear of a Greek government default, which would create havoc in world markets.  

Danmarks Nationalbank

Our final canary is the Danmarks Nationalbank. Unlike the demand for Swiss paper francs, the demand for Danish paper krone does not usually to spike during times of crisis. For instance, during the 2008 credit crisis demand remained muted. This leads me to believe that demand for paper krone provides the clearest indicator yet of the presence (or not) of the effective lower bound. I've charted the year-over-year change in Danish currency in circulation.

In the 55 days that have passed since the Danmarks National bank reduced its rates to -0.75% (February 5), there has been a sustained rise in the demand for cash, as the red data indicate. But I don't think we can describe it as anything out of the ordinary, at least not yet.

Interestingly, in late March the Nationalbank granted Danish banks some wiggle room by providing them with greater access to the Bank's 0% current-account facility. This small adjustment would have reduced Danish banks' incentives to emigrate from -0.75% deposits into cash. Was the central bank's decision to provide this wiggle room a response to private data showing that it had hit the effective lower bound? Who knows.

It may be worth noting even if a central bank finds itself at the effective lower bound, it can forestall the demand for large denomination notes by using moral suasion. Willem Buiter mentions this possibility in his recent note High Time To Get Low, but maintains we have no evidence of this sort of pressure. I'm tempted to agree with him. If either the Danish or Swiss central bankers have put informal embargoes on cash, we would have known about it by now.

The use of moral suasion to prevent large denomination banknote storage would effectively freeze the quantity of high value notes in circulation. In such a scenario, we'd expect the 1000 Sfr note to rise to a slight premium to face value, say 1050 Sfr in bank deposits for each 1000 Sfr in banknotes. Traders would be willing to pay this premium as long as the storage costs on high value notes are lower than the -0.75% penalty set by the SNB on deposits, thus allowing them to earn an excess return on their note holdings. As long as moral suasion remains successful in choking off Swiss banks' demand for cash, each subsequent cut by the SNB into ever deeper negative territory would drive the premium on notes higher. (Assiduous readers will recognize this as the second of three ways for a lazy central banker to escape a liquidity trap.)

In sum, we probably haven't hit the effective lower bound yet. Stay tuned.

Friday, April 17, 2015

John Cochrane is too grumpy about negative rates

John Cochrane has written two posts that question the ability to implement negative interest rates given the wide range of 0%-yielding escape hatches available to investors. These escapes include gift cards, stamps, tax & utility prepayments, and more. In a recent post entitled However low interest rates might go, the IRS will never act like a bank, Miles Kimball and his brother rebut one of Cochrane's supposed exits; the Internal Revenues Service. I've responded to Cochrane's other schemes here.

Think of Cochrane's exits as arbitrage opportunities. As nominal rates plunge into negative territory, the public gets to harvest these outsized gains at the expense of institutions that issue 0% nominal liabilities. The Kimballs' point (and mine here) is that because these institutions will lose money if they continue to issue these liabilities, they will implement policies to plug the holes. Cochrane's multiple exits aren't the smoking gun he takes them to be.

In a new post, Cochrane tries to salvage his argument by making an appeal to symmetry. He points out that in the symmetrical casea world with positive inflation and higher nominal rateswe don't actually observe people adopting the sort of behavior that Miles believes they would adopt in a negative rate world. So in practice, Cochrane doesn't believe that removing cash in order to implement negative interest rates will work.

This is a fair tactic to take. In general, people should demonstrate similar behavior whether nominal rates are positive or negative. However, is it true that in an environment with positive inflation and high nominal rates, institutions issuing liabilities (or those purchasing those liabilities) allow themselves to be systematically made the targets of arbitrage?

Take Cochrane's main example; gift cards. As I described here, once rates fall deep into negative territory, retailers will simply stop issuing gift cards since they won't care to earn a negative spread. Cochrane's appeal to symmetry implies that gift card issuers behave differently when rates are positive. Well let's imagine that rates are at 5%. An issuer of 0% gift cards is certainly not setting itself up to be arbitraged—in fact, given that it is funding itself at 0% in a 5% yield environment, it will be earning an excess return on each card issued. Nor will the liability-using public choose to subject itself to the money-losing obverse side of the trade. People can simply choose to avoid investing in 0% gift cards in favor of a 5% alternative. Likewise for the other liabilities that Cochrane mentions. Rather than prepaying taxes and earnings 0%, the public will pay at the last moment and harvest a 5% return until then. Instead of delaying the cashing of a check, they'll deposit it the day they receive it in order to earn interest.

So when interest rates are positive, people will try to avoid behaviour that allows them to be taken advantage of, whether they be an issuer or buyer or liability. Symmetrically, it follows that this same behaviour should prevail when rates are negative.

In his post, Cochrane seems to be changing the subject of the conversation from arbitrage to the indexing of contracts. His point is that during periods of positive inflation and high interest rates, nominal payments were not indexed to the nominal interest rate. His example is the IRS, which does not offer interest for early payment when market interest rates are high. Factually he is right. But this criticism is besides the point. The IRS doesn't offer interest to those who pay their taxes early because prepaid taxes aren't the government's main form of funding, treasury debt is. If the government's main form of financing *was* to offer savings accounts to tax payers, then you can be sure that those accounts would have to promise nominal payments that rise in line with the market's nominal interest rate—otherwise no one would open an account and the government would suffer a cash crunch. Nor would the government offer an excess nominal rate, since every American would exploit the situation and open an account—at the government's expense.

No one wants to be the dupe and end up on the wrong side of an arbitrage. If anyone is arguing for asymmetry, it is Cochrane. He needs to explain why liability issuers and users would exhibit such a degree of irrationality as to allow themselves to be exploited as rates fall into negative territory, but so rational as to avoid being exploited at positive rates.

Monday, April 13, 2015

A libertarian case for abolishing cash

Last week Citi's Willem Buiter published a note on the three ways to get rid of the effective lower bound to nominal interest rates, one of which is to abolish cash. He goes on to say that
politically, the abolition of currency would run into opposition from some of the legitimately cash-dependent poor and elderly, from those for whom the anonymity of cash is desired because they are engaged in illegal activities and from libertarians. The first constituency can be helped, the second can be ignored and the third one should take one for the team.
I think that Buiter is wrong to characterize libertarians as necessarily opposed to the abolition of cash. Their take on cash is probably (or at least should be) a bit more nuanced. Since libertarians generally advocate government withdrawal from lines of business like health care or liquor retailing, an exit of central banks from the cash business should be a desirable outcome. However, libertarians would likely bristle at an across-the-board banning of cash of the sort that Buiter advocates, preferring instead that private banks be allowed to issue cash even as central banks vacate that product niche.

A libertarian privatization of the provision of cash wouldn't be science fiction. Historically, private banks were intimately involved in the production of paper currency—so such a setup isn't without precedent. In modern times, the majority of banknotes that circulate in Scotland are issued by three private banks—the Bank of Scotland, the Royal Bank of Scotland, and the Clydesdale Bank, while in Hong Kong, the major commercial banks are charged with issuing currency.

We can imagine that Buiter might object to libertarian banknote privatization on the grounds that it contradicts his original reason for abolishing cash: to rid the world of the pesky effective lower bound. After all, if private banks continue to issue negotiable bearer instrument that pay a zero nominal interest rate, a central banker will continue to be plagued by the problem that he/she can't reduce interest rates below zero since everyone will flee into private banknotes. It's the same liquidity trap as before, with private currency to blame rather than central bank currency.

However, there would be one key difference. Private banks must abide by the Darwinian calculus of profit and losses, central banks don't have to. Take a world with privatized cash. A recession hits and the rate of return on capital falls plummets. At the same time, the central bank drops its deposit rate deep into negative territory. As a private bank tries to match with deposit rate reductions of its own, say to -2%, customers will convert negative yielding deposits into the bank's higher-yielding 0% bank notes. The bank, whose survival depends on a healthy spread between the rates on borrowing and lending, faces a sudden spike in borrowing costs to 0%, the rate on their cash base. Spreads will shrink, even invert. Bankruptcy looms.

In order to avert this disaster, private issuers will quickly institute limits on their cash business. This could involve adopting any one of Buiter's three remedies: 1) cancel their note issue; 2) impose a fee on cash, or; 3) remove the fixed exchange rate between deposits and cash. Thus,the lower bound probably wouldn't be a problem in a banking system characterized by privatized paper issuance. The necessity of maintaining a spread would force private banks to rapidly innovate one of these escapes come recession and negative nominal rates. Upon recovery, they can remove these limitations and continue with their regular cash business.

Imagine that private banks all choose the first option when nominal rates fall below zero, cancellation. With cash no longer in existence, banks will have succeeded in restoring their margins to health. The population, however, will have effectively lost their ability to make anonymous transactions. This puts a libertarian in a tough philosophical position. One the one hand, a cashless world poses a serious threat to personal liberty. John Cochrane calls it an "Orwellian nightmare," and Chris Dillow has referred to banning cash as "a grossly illiberal measure - the banning of capitalist acts between consenting adults."

On the other hand, if cash threatens a bank's existence, no libertarian would advocate the use of force to prevent said bank from exiting the business of cash provision. Capitalistic acts cannot be forced upon non-consenting adults, or, put differently, Jack's desire for anonymity-providing products doesn't justify Jill being put into chains in order to provide those products. Therefore, a withdrawal of cash by banks as nominal rates fall below zero, and the loss of anonymity that comes with it, is consistent with libertarianism.

So oddly, Buiter's proposed end point—a cancellation of cash—is very similar to what a libertarian end point could look like. In both cases, the respective institution will elect to withdraw cash from circulation because it interferes with its institutional prerogative. For a central bank, this mission boils down to the targeting of some nominal variable like inflation while in the case of a private bank it is its ability to earn a competitive return. That's not to say that a libertarian ought to support Buiter's abolition, only that the subject is more nuanced than it might seem upon a superficial reading.  

As a postscript, it's worth noting that neither Buiter's central banker nor a libertarian's private banker need go as far as abolishing cash in order to remove the effective lower bound. Buiter provides two other options, the best of which (in my opinion) is removing the fixed exchange rate between cash and deposits. Miles Kimball has gone through this option exhaustively. I've outlined some even less invasive, though not as effective, options here.

Related links: 

Does the zero lower bound exist thanks to the government's paper currency monopoly? (link)
Is legal tender an imposition on free markets or a free market institution? (link)
Bill Woolsey on how the private sector would withdraw cash at negative rates (link | link )
FTAlphaville: Buiter on the death of cash ( link )

Wednesday, April 8, 2015

Liquidity as static

In his first blog skirmish, Ben Bernanke took on Larry Summers' secular stagnation thesis, generating a slew of commentary by other bloggers. If the economy is in stagnation, the econ-blogosphere surely isn't.

I thought that Stephen Williamson had a good meta-criticism of the entire debate. Both Bernanke and Summers present the incredibly low yields on Treasury inflation protected securities (TIPS) as evidence of paltry real returns on capital. But as Williamson points out, their chosen signal is beset by static.

Government debt instruments like TIPS are useful as media of exchange, specifically as collateral, goes Williamson's argument. Those who own these instruments therefore enjoy a stream of liquidity services that gets embodied in their price as a liquidity premium. Rising TIPS prices (and falling yields) could therefore be entirely unrelated to returns on capital and wholly a function of widening liquidity premia. Bernanke and Summers can't make broad assumptions about returns on capital on the basis of market-driven yields without knowing something about these invisible premia. (Assiduous readers may remember that I've used a version of the liquidity premium argument to try to explain the three decade long bond bull market, as well as the odd twin bull markets in bond and equity prices.)

Riffing on Williamson, liquidity premia are a universal form of static that muddy not only bond rates but many of the supposedly clear signals we get from market prices. Equity investors, for instance, need to be careful about using price earnings ratios to infer anything about stock market valuations. The operating assumption behind something like Robert Shiller's cyclically adjusted PE (CAPE) measure is that rational investors apply a consistent multiple to stock earnings over time. When CAPE travels out of its historical average, investors are getting silly and stocks are over- or undervalued.

But not so fast. Since a stock's price embodies a varying liquidity premium, a rise in equity prices relative to earnings may be a function of changes in liquidity premia, not investor irrationality. Until we can independently price these liquidity services, CAPE is useless as a signal of over- or undervaluation, a point I've made before. Hush, all you Shiller CAPE acolytes.

Liquidity also interferes with another signal dear to economists and finance types alike; expectations surrounding future inflation. The most popular measure of inflation expectations is distilled by subtracting the nominal yield on 10-year Treasuries from the equivalent yield on 10-year TIPS. The residual is supposed to represent the value of inflation protection offered by TIPS. But it is a widely known fact that this measure is corrupted by the inferior liquidity in TIPS markets. See commentary here, here, and here. The upshot is that a widening in TIPS spreads—which is widely assumed to be an indicator of rising inflation expectations—could be due to a degeneration  improvement in the liquidity of TIPS relative to the liquidity of straight Treasuries.

Interestingly, the Cleveland Fed publishes a measure of inflation expectations that tries to "address the shortcomings" of rates derived from TIPS by turning to data from a different source: inflation swaps markets. In an inflation swap, one party pays the other a fixed rate on a nominal amount of cash while the other returns a floating rate linked to the CPI. Given the market price of this swap, we can extract the market's prediction for inflation. According to the people who compile the Cleveland Fed estimate, inflation swaps are less prone to changes in liquidity than TIPS yields, thus providing a true signal of inflation expectations.

But how can that be? Surely the prices of swaps and other derivatives are not established independently of market liquidity. After all, like stocks and bonds, derivatives are characterized by bid-ask spreads, buyers strikes, and runs. Sometimes they are easy to buy or sell, sometimes difficult. When I first thought about this, it wasn't immediately apparent to me what liquidity premia in derivative markets would look like. With bond and equity markets, its easy to determine the shape and direction of the premium. Since liquidity is valuable, buyers compete to own liquid stocks and bonds while sellers must be compensated for doing without them. A premium on top of a security's fundamental value develops to balance the market.

Derivatives are different. Take a call option, where the writer of the option, the seller, provides the purchaser of the option the right to buy some underlying security at a certain price. In theory, the more liquid the option, the higher the price the purchaser should be willing to pay for the option. After all, a liquid option can be sold much easier than an illiquid one, a benefit to the owner. But what about the seller? I risk repeating myself here, but a seller of a stock or bond will require a *higher* price if they are to part with a more liquid the security. However, in the case of the option, the writer (or seller) will be willing to accept a *lower* and inferior price on a liquid option. After all, the writer will face more difficulties backing out of their commitment (by re-selling the option) if it is illiquid than if it is liquid.

This creates a pricing conundrum. As liquidity improves, the option writer will be willing to sell for less and the purchaser willing to buy for more. Put differently, the value that the writer attributes to the option's liquidity and the concomitant liquidity premium this creates drives the option price down, while the value the purchaser attributes to that same liquidity engenders a liquidity premium that drives the option price up. What is the net effect?

I stumbled on a paper which provides an answer of sorts (pdf | RePEc). Drawing on data from OTC options markets, the authors finds that illiquid interest rate options trade at higher prices relative to more liquid options. This effect goes in the opposite direction to what is observed for stocks and bonds, where richer liquidity means a higher price. The authors' hypothesis is that the liquidity premium of an option is set by those investors who, on the margin, are most concerned over liquidity. Given the peculiarities of OTC option markets, this marginal investor will usually be the option writer (or seller), typically a dealer who is interested in reversing their trades and holding as little inventory as possible, thus instilling a preference for liquidity. Buyers, on the other hand, tend to be corporations who are willing to buy and hold for the long term and are therefore less concerned with a fast getaway. The net result is that for otherwise identical call options, the overriding urgency of dealers drives the price of the more liquid option down and illiquid one up.

Anyone who has dabbled in futures markets may see the similarity in the story just recounted to a much older idea, the theory of normal backwardation. The intuition behind normal backwardation is that a futures contract, much like a call option, has two counterparties, both of whom need to be rewarded with a decent expected return in order to encourage them to enter into what is otherwise a very risky bet. If both require this return, then how does an appropriate "risk premium" get embodied in a single futures price?

None other than John Maynard Keynes hypothesized that the two counterparties to a futures trade are not entirely symmetrical. Hedgers, say farmers (who are normally short futures), simply want a guaranteed market for their goods come harvest and are willing to provide speculators with the extra return necessary to induce them to enter into a long futures position. Farmers create this inducement by setting the current price of a futures contract a little bit below the expected spot price upon delivery, thus providing speculators with a promise of extra capital returns, or a risk premium. That's why Keynes said that futures markets are normally backwardated.

Options writers who desire the comforts of liquidity are playing the same game as farmers who desire a guaranteed price. They are inducing counterparties to take the other side of the deal, in this case the liquid one, by pricing liquid options more advantageously than illiquid but otherwise identical options. And while I don't know the peculiarities of the various counterparties to an inflation swap, I don't see why the same logic that applies to options wouldn't apply to swaps.

So returning to the main thread of this post, just as the signals given off by TIPS spreads are beset by interference arising from liquidity phenomena, the signals given off by inflation swaps are also corrupted. A widening in inflation swap spreads could be due to changing liquidity preference among a certain class of swap counterparties, not to any underlying change in inflation expectations. Its not a clear cut world.

What about the most holy of signals given off by derivative markets: the odds of default as implied by credit default swap spreads? A CDS is supposed to indicate the pure credit risk premium on an underlying security. But if the marginal counterparty on one side of a credit default swap deal is typically more interested in liquidity than the other counterparty, then CDS prices will include a liquidity component. According to the paper behind the following links ( pdf | RePEc ), it is the sellers of credit default swaps, not the buyers, who typically earn compensation for liquidity, the theory being that sellers are long-term players with more wealth than buyers. The paper's conclusion is that CDS spreads cannot be used as frictionless measures of default risk.

Liquidity is like static, it blurs the picture. The clarity of the indicators mentioned in this post—Bernanke & Summers' real interest rates, stock market price earnings ratios, inflation expectations implied by both TIPS and swap markets, and finally the odds of default implied in corporate default swap spreads—are all contaminated by liquidity premia that vary in size over time. Models created by both economists and financial analysts contain abstract variables that map to these external data sources. I doubt that this data is irrevocably damaged by liquidity, but it may be warped enough that we should be wary about drawing strong conclusions from models that depend on them as input.

Before I slide too far into economic nihilism, there may be a way to resuscitate the purity of these indicators. If we can calculate the precise size of liquidity premia in the various markets mentioned above, then we can clean up the real signals these markets give off by removing the liquidity static.

One way to go about calculating the size of a liquidity premium is by polling the owners of a given security how much they must be compensated for doing without the benefits of that security's liquidity for a period of time. Symmetrically, a potential owner of that security's liquidity is queried to determine how much they are willing to pay to own those services. The price at which these two meet represents the pure liquidity premium. Problem solved. We can now get a pure real interest rate, a precise measure of inflation expectations, a true measure of credit default odds, or a liquidity-adjusted price-to-earnings multiple.

Unfortunately, its not that easy. The only way to properly discover the price at which a buyer and seller of a particular instrument's liquidity services will meet is by fashioning a financial contract between them,  a financial derivative. These derivatives will trade in a market for liquidity or 'moneyness' that might look something like this. And therein lies the paradox. Much like the option and CDS of our previous example, this new derivative will itself be characterized by its own liquidity premium, thus impairing its ability to provide a clean measure of the original instrument's liquidity premium. We could fashion a second derivative contract to measure the liquidity premium of the first derivative contract, but that too will be compromised by its own liquidity premium, taking us down into an infinite loop of imprecision.

So... back to economic nihilism. Either that or a more healthy skepticism of those who confidently declare the economy to be in stagnation or the stock market to be a bubble. After all, there's a lot of static out there.

Note: David Beckworth has also written about the difficulties of using bond yields as indicators of secular stagnation. (1)(2)(3). And now Nick Rowe has a post on secular stagnation and liquidity.

Saturday, March 28, 2015

The bond-stock conundrum

Here's a conundrum. Many commentators have been trying to puzzle out why stocks have been continually hitting new highs at the same time that bond yields have been hitting new lows. See here, here, here, and here. On the surface, equity markets and bond markets seem to be saying two different things about the future. Stronger equities indicate a bright future while rising bond prices (and falling yields) portend a bleak one. Since these two predictions can't both be right, either the bond market or the stock market is terribly wrong. It's the I'm with stupid theory of the bond and equity bull markets.

I hope to show in this post that investor stupidity isn't the only way to explain today's concurrent bull market pattern. Improvements in financial market liquidity and declining expectations surrounding the pace of consumer price inflation can both account for why stocks and equities are moving higher together. More on these two factors later.

1. I'm with stupid

The I'm with stupid view goes something like this...

If investors expect strong real growth for the next few decades, a new bond issue has to provide a competitive coupon in order to attract capital. Soon after the bond is issued, economic growth stagnates and the economy's expected real rate of return falls. The bond's coupon, originally rated for a much healthier economy, has become too good for the new slow-growth environment. The price of the bond has to rise relative to its face value (thus counterbalancing the juicy coupon with a guaranteed capital loss) so that its overall rate of return falls to a level commensurate with the economy's lower real rate of return. That's why rising bond prices are often a sign of a bleaker future.

As for equities, that same decline in the real rate of return will result in a fall in prices. A stock is a claim on whatever profits remain after interest, and lower real growth means a smaller remainder. No wonder then that a number of investment commentators believe that the modern rise of stock and bond prices requires one set of investors to be acting irrationally; after all, things can't be simultaneously better and worse off in the future. Either that or arbitrage between the two markets is simply impossible, say because large actors like the Fed are rigging the market. Whatever the case, concurrent bull markets implies a giant market inefficiency, as Diego Espinosa has described it.

Massive inefficiency isn't a very satisfying theory for the twin rises in bond and stock markets. Thankfully, we don't need to resort to changes in real growth rates to explain securities price changes. Let's explore two other factors that could be driving the concurrent bull market pattern:

2. Falling inflationary expectations and concurrent bull markets

Assume that the real growth rate is constant over time but inflation expectations decline. The real value of all flows of coupon payments from existing bonds are suddenly more valuable, causing a one-time jump in bond prices. If inflation expectations consistently fall over time, then a bull trend in bond prices will emerge. This is standard stuff.

And stocks? What many people don't realize is that those same declining inflation expectations will set off a bull market in equities as well. The general view is that a firm's bottom line waxes or wanes at the same pace as inflation, the result being that real stock returns are invariant to inflation. Corporate shares are supposed to be hedges against inflation.

This is (almost always) wrong, a point I've made before (here and here). Let me take another stab at it. In short, thanks to the interaction between historical cost accounting and the way taxes are collected, rising inflation expectations will boost a firm's real future tax burden, reducing real cash flows and therefore stock prices. Falling expectations about inflation act like a tax cut, increasing real cash flows and stock prices.

For folks who want to work through the logic, what follows is a numerical example. Take a very simple firm which incorporates itself, buys inventory and a machine with the cash raised, operates for four years, and dissolves itself. At the end of each year it pays out all the cash it has earned to its shareholders. At the outset, the company buys 40 unfinished widgets for $60 each. Over the course of its life, it expects to process 10 widgets a year and sell the finished product at a real price of $100. In order to process the unfinished widgets, it buys a widget upgrader for $500. The upgrader is used up, or depreciated, at a rate of $125 year so that it will be useless after year four. Since the company will have also depleted its inventory of unfinished widgets by that time, it has nothing left over after the fourth year.

The first table shows the anticipated cash flows that will be paid to shareholders after taxes have been rendered to the tax authority, assuming 0% inflation over the course of four years. The cash amounts to an even $876.25 a year.

Let's boost the expected inflation rate to 1% (see table below). The real value of cash flows starts out at $876.25 in year one but steadily declines, hitting $866.66 by year four. Shareholder get less real cash flows than they did in a stable inflation environment.

On the other hand, if we ratchet down expected inflation to -1%, the real value of cash flows starts out at $876.50 in the first year but climbs to $886.24 by the end of year four. Shareholders enjoy a larger real flow cash payments than they did in either the stable or the rising expected inflation environments. If cash dividends are immediately spent on consumption, this means that shareholders enjoy the greatest flow of consumption when inflation expectations are falling.

A reduction in expected inflation will cause a one-time jump in our company's share price. If these reductions in expected inflation occur consistently over time, we get a series of jumps in the company's share price, or a bull market.

The core intuition behind this result is that under historical cost accounting, a company's cost of goods sold and its depreciation expenses are both fixed in time. Cost of goods sold is valued on a first-in-first out basis, which means the price of the oldest good is used to value unit costs (in our case, $60), while depreciation is calculated as a fixed percentage of a machine's original purchase price. When inflation is stable, this is unimportant. But once expected inflation rises, the firm's costs grow stale and can no longer keep up with its anticipated revenues, the result being artificially higher pre-tax accounting profits and a larger tax bill. These bloated future tax bills drain cash from the firm, resulting in lower expected cash payouts to shareholders over the life of the firm.

When expected inflation falls, the firm's anticipated revenues shrink relative to its costs, the result being lower future pre-tax profits and a lighter tax bill. Less cash filters out of the firm, leaving more cash in the kitty for shareholders to enjoy at the end of each year.

The table below shows how our firm's real tax bill varies across each of these scenarios:

So a reduction in expected inflation is (almost always) good for equity prices as it amounts to a tax cut. Why have I inserted a caveat? When a company is indebted, lower-than-expected inflation will increase the real burden of that debt. If its debt load is heavy, the debt effect may outweigh the combined effects of cost of goods sold and depreciation. One reason why falling inflation expectations in Japan during the 1990s and 2000s didn't result in an equity boom is that Japanese companies tend to be far more indebted than companies in the rest of the world. (This may also explain why Japanese stocks outperformed U.S. stocks during the inflationary 1970s.) For most of the world's markets a reduction in expectations surrounding the rate of inflation is an ideal situation for equities.*

What do we know about the actual shape of inflation expectations? In general people have been marking their expectations downwards since the early 1980s, a trend that has been amplified since the credit crisis as central banks around the developed world have consistently undershot their inflation targets. We thus have the underpinnings for a concurrent bull market in stocks and bonds, driven by falling inflation expectations.

3. Liquidity and the concurrent bull market pattern

Let's move on to our second factor. Assuming that the real growth rate and expected inflation both stay constant, we can also generate concurrent bull markets in stocks and bonds by simultaneously improving their liquidity. Innovations in market infrastructure over the years have made it easier to buy and sell financial assets. Investors can increasingly use financial assets as media of exchange, swapping them directly for other financial assets rather than having to go through deposits as an intervening medium. Think buzz words like re-hypothecation and collateral chains.

As financial assets become more liquid, a larger portion of their overall return comes in the form of a non-pecuniary liquidity yield. All things staying the same, investors must cough up a larger premium in order to enjoy this liquidity-augmented return, resulting in a one time jump in asset prices. Consistent improvements to liquidity will result in a step-wise asset bull market.

I've written here about the ongoing liquidity enhancements in equity markets, and speculated here that thirty-year bull market is bonds is (partly) a function of improved bond liquidity. In the same vein, Frances Coppola once penned an article noting that when everything becomes highly liquid, the yield curve is flat, reducing returns across all classes of financial assets (a flattening of the yield curve implies a jump in the price of long term bonds).

While I think that liquidity-improving innovations in market technology and declining inflation expectations can explain a good chunk of the stock bull market, I don't think they can't quite explain as much of the secular rise in bond prices. After all, market interest rates haven't just plunged. In many cases both nominal and real bond interest rates have gone negative.

We can salvage this problem by resorting to another liquidity-based explanation for why bond investors are willing to accept negative returns. Government bonds provide a unique range of liquidity services in their role as a financial media of exchange, a role that cannot be replicated by central bank reserves or any other medium of exchange. Reserves, after all, can only be held by banks, and corporate bonds aren't safe enough to serve as universally-accepted collateral. However, governments have gone into austerity mode, reducing the flow rate of bonds coming onto the market. At the same time, central banks are buying up and removing government bonds from circulation. As a result, the supply of unique liquidity services provided by bonds is growing increasingly scarce, forcing investors to bid up the price of these services. Liquidity premia are high. So a negative real return on bonds may be a reflection of the the hidden fee that bond investors are willing to pay to own a government bond's flow of liquidity returns. I've written about this here.

In sum, the I'm with stupid theory, with its implication of massive inefficiencies, shouldn't be our only theory for concurrent bull markets. Asset prices move for many reasons, not just changes in expected real growth. Bond and equity investors may be reacting non-stupidly to shifting liquidity patterns and declining inflation expectations, the result being a steady bidding up of the prices of both assets.

*If you are interested in the difference between Japan and the rest of the world, here are some papers worth investigating: 

The Taxation of Income from Capital in Japan, Kikutani and Tachibanaki (pdf)
The Cost of Capital in the U.S. and Japan: A Comparison, Ando and Auerbach (pdf)
Are Japanes Stock Prices to High. French and Poterba (pdf)

Wednesday, March 18, 2015

Hawk, Doves, and Canaries

Central bankers are usually classified as either hawks or doves. This post is devoted to a third and rare breed; today's monetary policy canaries. Having taken their respective deposit rates to -0.75%, deeper into negative territory than any other bank in history (save the Swedes), the Swiss National Bank and Denmark's Nationalbank are the canaries of the central banking world, plumbing depths that everyone assumes to be dangerous. Other central bankers, in particular the ECB's Mario Draghi, will no doubt be watching the Swiss and Danes quite closely. The information these two nations generate as they go deep into the bowels of negative rate territory will give a good indication of the level to which the others can safely reduce their own rates before hitting their respective effective lower bounds.

That there is an effective lower bound to rates stems from the fact that at some negative nominal interest rate, everyone will choose to convert deposits into cash, preferring to pay storage and handling costs on the underlying paper instrument than enduring a negative interest penalty on the electronic equivalent. Once this process starts, a central bank will be unwilling to push rates much lower given the possibility that the economy's entire deposit base gets converted into paper.

Last week Danish central banker Lars Rohde told the WSJ that while there is some lower bound for negative interest rates, "we haven't found it yet." What Rohde was basically saying is that the marginal storage costs of Danish cash are higher than -0.75%, Denmark's current monetary policy rate. If costs were lower, than Denmark's largest and most efficient cash hoarders, Danish banks, would have already rushed to convert their deposits held at the Nationalbank into banknotes—and Rohde would have found his as-yet inactive lower bound. Given his confident tone, Rohde must not be seeing much demand for banknotes. He would know. As his nation's central banker, he's privy to real time information on the quantity of cash that the central bank is being called upon to print up and provide to commercial banks.

We can get a rough feel for the data that Rohde is seeing. The chart below shows the year-over-year percent increase in end-of-month Danish cash and coin outstanding. The data is current to the end of February, eighteen days ago. Given that Denmark's deposit rate was initially reduced to -0.5% on January 29 and then to -0.75% on February 5, the data affords us an insight into the first thirty or so days of Danish cash demand at ultra low interest rates.

The chart shows that the yearly rate of growth in cash outstanding has accelerated slightly but is well within its normal range. What does this tell us about paper storage costs? Let's crunch some numbers. Danish banks currently have around 350 billion krone in funds on deposit at the Danish Nationalbanken in the form of certificates of deposit. This amounts to about US$50 billion. The central bank's -0.75% interest rate imposes yearly charges of around 2.5 billion krone, or US$375 million, on those deposits. In choosing to hold funds at the central bank, Danish banks are revealing that the cost of handling and storing paper cash must be somewhere above $375 million a year, else they'd have already started to convert into the cheaper alternative.

Keep in mind that this illustrates just thirty days with deep negative rates. With cash use in Denmark having been stagnant for a number of years (see chart here), vault space may have been re-purposed for other uses—maybe employees have been parking their commuter bikes in unused vaults or storing old bank documents in them. It could take time for vaults to be cleaned up. If so, a dash into cash could simply be delayed by a few weeks.

When Denmark hits its effective lower bound, what will the above chart look like? The 350 billion krone in deposits that banks currently keep at the central bank would quickly be converted into cash. Since Denmark currently has just 65 billion krone in notes and coin in circulation, we'd see a quintupling in cash outstanding. For comparison's sake, this would dwarf previous episodes of strong krone cash demand, like Y2K.

And what of our other canary, the SNB? The Swiss, so timely on matters of transport, don't think that up-to-date central banking data is important. The SNB's most recent data on cash outstanding is too stale to give a good idea how the Swiss have reacted so far to -0.75% rates. All we've got is anecdotes. This article reports that a Swiss pension fund attempted to withdraw a portion of its investments from its bank and hold it in a vault, thus saving 25,000 francs per 10 million francs after storage & handling costs, the implication being that these costs run around 0.5% a year. We'll have to wait for more data to come out of Switzerland before we can gauge whether it is at its effective lower bound.

What we do know is that Switzerland's bound will be much tighter than Denmark's. That's because while Denmark's largest denomination note is the 1000 krone note (worth about US$141), Switzerland's largest note is the 1000 franc note (worth about US$993.) That makes a US$1 million bundle of Danish notes seven times more bulky than that same bundle of Swiss notes, resulting in higher storage costs. This has important implications, since Mario Draghi's ECB, which issues a 500 euro note (worth US$530), likely has an effective lower bound that lies somewhere in between these two.

All of these data points may seem quite being arcane, but they have a very real policy significance. They're the difference between a central bank running out of interest rate ammunition, or buying itself an extra ten 10 basis point rate cuts.

Thursday, March 12, 2015

The final chapter in the Zimbabwe dollar saga?

Here's an interesting fact. Remember all those worthless Zimbabwe paper banknotes? The Reserve Bank of Zimbabwe (RBZ), Zimbabwe's central bank, is officially buying them back for cancellation. According to its recent monetary policy statement, the RBZ will be demonetizing old banknotes at the "United Nations rate," that is, at a rate of Z$35 quadrillion to US$1. Stranded Zimbabwe dollar-denominated bank deposits will also be repurchased.

As a reminder, Zimbabwe endured a hyperinflation that met its demise in late 2008 when Zimbabweans spontaneously stopped using the Zimbabwe dollar as either a unit of account or medium of exchange, U.S. dollars and South African rand being substituted in their place. Along the way, the RBZ was used by corrupt authorities to subsidize all sorts of crazy schemes, including farm mechanization programs and tourism development facilities.

Upon hearing about the RBZ's buyback, entrepreneurial readers may be thinking about an arbitrage. Buy up Zimbabwe bank notes and fly them back to Zimbabwe for redemption at the RBZ's new official rate, making a quick buck in the process. But don't get too excited. The highest denomination note ever printed by the RBZ is the $100 trillion note. At the RBZ's demonetization rate, one $100 trillion will get you... US$0.003. With these notes selling for US$10 to $20 as collectors items on eBay, forget it—there's no money to be made on this trade. If you've already got a few $100 trillion Zimbabwean notes sitting in your cupboard, you're way better off hoarding them than submitting them to the RBZ's buyback campaign.

But this does give us some interesting data points about the nature of money. Last year I wrote two posts on the topic of whether money constituted an IOU or not. With the gold standard days long gone, central banks no longer offer immediate redemption into some underlying asset. But do they offer ultimate redemption into an asset? A number of central banks—including the Bank of Canada and the Federal Reserve—make an explicit promise that notes constitute a first claim or paramount lien on the assets of the central bank. This language implies that banknotes are like any other security, say a bond or equity, since each provides their owner with eventual access to firm assets upon liquidation or windup of the firm.

George Selgin is skeptical of the banknotes-as-security theory, replying that a note's guarantee of a first claim on assets is a mere relic of the gold standard. However, the Bank of Canada was formed after Canada had ceased gold convertibility. Furthermore, modern legislation governing central banks like the 2004 Central Bank of Iraq (CBI) Law declares that banknotes "shall be a first charge on the assets of the CBI." [See pdf]. So these promises certainly aren't relics of a bygone age. The Zimbabwean example provides even more evidence that a banknote constitutes a terminal IOU of sorts. After all, Zimbabwean authorities could have left legacy Zimbabwe dollar banknotes to flap in the wind. But for some reason, they've decided to provide an offer to buy them back, even if it is just a stink bid.

Given that banknotes are a type of security or IOU, how far can we take this idea? For instance, analysts often value a non-dividend paying stock by calculating how much a firm's assets will be worth upon break up. Likewise, we might say that the value of Zimbabwean banknotes, or any other banknote, is valued relative to the central bank's liquidation value, or the quantity of central bank assets upon which those notes are claim when they are finally canceled. If so, then the precise quantity of assets that back a currency are very important, since any impairment of assets will cause inflation. This is a pure form of the backing theory of money.

I'm not quite willing to take this idea that far. While banknotes do appear to constitute a first claim on a central bank's assets, the central bank documents that I'm familiar with give no indication of the nominal quantity of central bank assets to which a banknote is entitled come liquidation. So while it is realistic to say that the Reserve Bank of Zimbabwe always had a terminal offer to buy back Zimbabwe dollars, even during the awful hyper-inflationary period of 2007 and 2008, the lack of a set nominal offer price meant that the value of that promise would have been very difficult to calculate. More explicitly, on September 30, 2007, no Zimbabwean could have possibly know that, when all was said and done, their $100 trillion Zimbabwe note would be redeemable for only US$0.003. The difficulty of calculating this terminal value is an idea I outlined here, via an earlier Mike Friemuth blog post.

While the final chapter of the Zimbabwe dollar saga is over, the first chapter of Zimbabwe's U.S. dollar standard has just begun. Gone are the days of 79,600,000,000% hyperinflation. Instead, Zimbabweans are experiencing something entirely new, deflation. Consumer prices have fallen by 1.3% year-over-year, one of the deepest deflation rates in the world and the most in Africa. With prices being set in terms of the U.S. dollar unit of account, Zimbabwean monetary policy is effectively held hostage to the U.S. Federal Reserve's 12 member Federal Open Market Committee. Most analysts expect the Fed to start hiking rates this year, so I have troubles seeing how Zimbabwean prices will pull out of their deflationary trend. Few people have experienced as many monetary outliers as the citizens of Zimbabwe over such a short period of time. I wish them the best.

Saturday, March 7, 2015

Paul Krugman contemplates the lower bound

Paul Krugman has two posts discussing the effective lower bound to interest rates. The first I agree with, albeit with a caveat, and the other I don't.

In his first post Krugman takes Evan Soltas to task for including not only storage costs in his calculation of the effective lower bound, but also the extra convenience yield provided by deposits. Krugman's point is that once people are "saturated" with liquidity, as they seem to be now, then forgoing the liquidity of a short term marketable debt instrument (like a deposit) costs them nothing. If so, then the lower bound to nominal interest rates is solely a function of storage costs.

I agree with Krugman on this count. Take the 2 1/8% Nestle bond maturing May 29, which may be one of the first corporate bonds in history to trade at negative rates:

If it costs 0.50%/year to store and handle Swiss paper currency, then the rate on a Nestle bond can't fall below -0.50%. If it trades at -0.55%, an arbitrageur will contract to borrow the bond until it matures on May 29, sell it now, and convert the proceeds into 0% yielding SFr 1000 banknotes (these notes eventually being used to repay the bond lender). Our arbitrageur will incur 0.50%/year in storage costs while getting 0.55%/year from the bond lender, earning a risk-free return of 0.05%. Competition among arbitrageurs to harvest these gains will prevent Nestle's bond yield from falling much below storage costs.

However, here's the caveat. Krugman is assuming that liquidity is a homogeneous good. It could very well be that "different goods are differently liquid," as Steve Roth once eloquently said. The idea here is that the sort of conveniences provided by central bank reserves are different from the those provided by other liquid fixed income products like deposits, notes, and Nestle bonds. If so, then investors can be saturated with the sort of liquidity services provided by reserves (as they are now), but not saturated by the particular liquidity services provided by Nestle bonds and other fixed income products.

Assuming that  Nestle bonds are differently liquid than central bank francs, say because they play a special roll as collateral , then Soltas isn't out of line. Once investors have reached the saturation point in terms of central bank deposits, the effective lower bound to the Nestle bond isn't just a function of the cost of storing Swiss paper money, but also its unique conveniences.

This changes the arbitrage calculus. Our arbitrageur will now have to pay a fee to the lender of the Nestle bonds in order to compensate them for services forgone. Let's say the cost of borrowing the bond is 0.25%/year. Shorting the bond once it hits -0.55%, paying the borrowing cost of 0.25%, and storing the proceeds at a cost of 0.50% a year results in a loss of 0.20%. With the arbitrage being unprofitable, the Nestle bond can theoretically fall further than in our previous example before it hits the effective lower bound (specifically, its lower bound is now -0.75%).

How realistic is it that different goods are differently liquid? Since everybody seems to turn to Michael Woodford as the ultimate moderator of all questions monetary, here he is in his famous Jackson Hole paper [pdf] talking about the potential for different assets to have different types of convenience yields: might suppose that Treasuries supply a convenience yield of a different sort than is provided by bank reserves, so that the fact that the liquidity premium for bank reserves has fallen to zero would not necessarily imply that there could not still be a positive safety premium for Treasuries.
Unfortunately, it's almost impossible to know for sure whether the liquidity services of a Nestle bond, or any other bond for that matter, are valued on the margin when people are already saturated in reserves. This is because there is no market for liquidity. If there was, then we could back out the specific price that investors are currently placing on a given bond's liquidity services, say by asking them to put a value on how much they need to be compensated if they are to forgo those services for a period of time. I've mentioned liquidity markets in many different posts. But I digress.

Krugman ends his first post saying that "I am pinching myself at the realization that this seemingly whimsical and arcane discussion is turning out to have real policy significance." But in his second post he backtracks, saying that a "minus x lower bound" isn't all that special in term of policy, implying that x (i.e. storage cost) is low and likely to diminish thanks to financial innovation. Here I disagree. Once a central bank has reduced rates to the point at which it is facing a run into paper storage, it can turn to a new tool to buy itself even more room to the downside for rate cuts: the manipulation of x, or the storage costs of cash.

To conclude, we've all found out by now that there isn't a zero lower bound. Instead it's a minus x lower bound. The next step is to realize that x isn't set in stone, it can itself be made into a tool of monetary policy.

Wednesday, March 4, 2015

Why so down?

If you've been reading Bill Gross's last few letters, you'll know that he's been a bit grumpy of late. It's that dang new trend that has hit bond markets, negative interest rates. Gross has been using words like incredible, surreal, and inconceivable to describe their arrival.Negative nominal bond rates certainly seem odd. Just look at the chart below, which illustrates what could very well be the two lowest-yielding bonds in the world, maybe all of history: the 3.75% Swiss government maturing in July 10, 2015 and the 4% Danish government bond maturing November 15, 2015. But is the idea of a negative rates really so strange?

Gross blames negative rates on central bankers who "continue to go too far in their misguided efforts to support future economic growth," in doing so "distorting" capitalism's rules. He's not alone; plenty of people claim that without autocratic price fixers like the SNB's Tommy Jordan and the Danmarks Nationalbank's Lars Rohde, rates would rapidly to rise to a more natural level like 1% or 2%.

Not necessarily. Even an economy without meddling central banks could be characterized by negative nominal rates from time to time, or, stealing from Tony Yates; "a negative rate doesn't distort capitalism, it IS capitalism."

Let's exorcise central bankers entirely from the economy. Imagine that we live in a world where things are priced in grams of gold. People walk around with pockets full of gold dust and a set of scales to measure the appropriate pinch necessary to pay for stuff. In this world, we all have a choice between two states: 1) we can hold gold dust in our pockets or 2) we can lend the dust to someone else for a period of time in return for an IOU. (Let's assume that the borrower is risk free.)

Each state has its own advantages and disadvantages. If we hold the gold dust in our pockets, we'll have instant access to a highly-liquid medium of exchange. Unlike illiquid media of exchange, liquid media provide us with the means to rapidly re-orient ourselves come unexpected events. With gold dust on hand we can purchase the necessities that allow us to cope with sudden problems or to take advantage of lucky breaks. At the end of the day, we may never actually use our gold to purchase things, preferring to keep it horded under our mattress. Even so, it hasn't sat their idly, but has provided us with a stream of consumption over time. The discounted stream of comfort that liquidity provides represents the total expected return on gold dust-held.

If we choose the second state and lend out our gold dust, we lose access to this liquidity and thus forfeit the expected stream of comfort that gold dust provides. Because we need to be compensated for this loss, a borrower will typically pay the lender a fee, or interest. But gold dust is burdensome. It is heavy and must be arduously weighed out and stored overnight in expensive vaults. IOUs, on the other hand, are a breeze to store. By offering to take our gold dust off our hands for a year or two, a borrower agrees to unburden us of storage expenses while providing us with a feather-light IOU in return.

So on the margin, when choosing between gold dust and an IOU, we are comparing the low storage costs of the illiquid IOU against the extra liquidity of cumbersome gold dust.

What might make rates turn negative in our central bankless gold dust world? Here are two ways:

1. Rising storage costs

Say that the costs of storing and handling gold dust grow substantially. At some much higher carrying cost, rather than requiring a fee from a borrower (i.e. positive interest) a lender will willingly pay the borrower a fee (i.e. will accept a negative interest rate) for the benefit of being temporarily unburdened of their gold dust. The loss of liquidity that the loan of gold dust imposes on the lender is entirely overwhelmed by the benefits of being freed from onerous storage costs. We get a sub-zero interest rate.

2. A narrowing liquidity gap

The second way to arrive at sub-zero interest rates is to narrow the vast gap between the respective liquidity returns on gold dust and IOUs. There are a few ways to go about this. Imagine that retailers who had previously only accepted gold dust as payment begin accepting IOUs too. Simultaneously, borrowers innovate by printing their paper IOUs in round numbers, making them far easier to count than grams of dust. All of this narrows the liquidity gap by improving the liquidity of IOUs. If the liquidity of IOUs improves so much that it exceeds the liquidity of the gold dust, an IOU effectively provides a greater stream of relief-providing services than gold. When this happens, lenders will clamour to pay a fee in order to lend their gold dust, since the superior optionality that an IOU provides is valuable to them. This fee represents a sub-zero interest rate.

Another way to narrow the vast liquidity gap between gold dust and IOUs is to create so much liquidity that, on the margin, liquidity becomes like air; it has no value. Neither gold dust nor IOUs can offer a superior liquidity return if society no longer puts any price on liquidity. In this situation, the interest rate on IOUs is purely a function of storage costs. Since an IOU will typically be less costly to store than the dust, the borrower of gold will typically receive a fee from the lender, a negative interest rate, in order to cover storage costs. Paul Krugman takes this tack here to explain negative rates.

So in the end, we can get negative nominal interest rates without central bankers. How far below zero can interest rates fall in a gold dust world? At least as low as the cost of storing gold dust and the degree to which the marginal value of an IOUs liquidity exceeds that of gold dust. Obviously we don't actually use gold dust in the real world, but the same principles apply to a cash-using economy. The theory behind negative rates isn't so surreal after all, Mr. Gross.

Some links to read:

Beyond bond bubbles: Liquidity-adjusted bond valuation by JP Koning [link]
What's the Actual Lower Bound? by Evan Soltas [link]
How Negative Can Rates Go? by Paul Krugman [link]
It turns out that the US was never at the zero bound by Scott Sumner [link]
What gold's negative lease rate teaches us about the zero-lower bound by JP Koning [link]