Tuesday, March 27, 2018

More fiatsplainin': let's play fiat-or-not

The (Great) Tower of Babel, 1563, Bruegel the Elder. "Therefore is the name of it called Babel; because the Lord did there confound the language of all the earth"

People bandy the term fiat currency around a lot, but what exactly does it mean? None of us wants to live in a Babel where people use fiat to indicate twenty different thing. So let's try to zero in on what most people mean by playing a game called fiat-or-not. I will describe a monetary system as it evolves away from a pure commodity arrangement and you will tell me when it has slipped into being a fiat system. (The technique I am using in this post cribs from a classic Nick Rowe post).

So let's start the game.

1) An economy in which gold coins circulate as the medium of exchange.

Fiat or not? I think we can all agree that there is nothing fiat at all here. (For simplicity's sake let's assume for the duration of this post that taxes can be paid with anything, and that there is no legal tender.)

2) A government-owned central bank begins to issue banknotes that are redeemable into a fixed amount of gold. Owners of banknotes need only line up at the central bank's redemption window to convert their $1 notes into 1 gram of the yellow metal. The central bank ensures that its vaults contain 100% gold backing for its notes.

Fiat or not? Some people associate fiat with the invention of paper money or IOUs, but in general I don't think very many of us would say that these banknotes qualify as fiat.

3) The central bank sells off a chunk of its gold and invests in safe bearer bonds. Its banknotes are no longer 100% backed by gold coins, but are backed 70% bonds/30% gold. The central bank continues to redeem notes on demand with gold at a rate of $1 to 1 gram.

Say the public suddenly wants to hold more coins. A lineup develops at the central bank's redemption window and eventually the central bank uses up its coin reserves as it meets redemption requests. To continue meeting additional requests, it need only sell some of the low-risk bonds from its vault and use the proceeds to buy additional gold coins.  

Fiat or not? Since low-risk bonds have now become part of the backing for the banknote issue, a few readers may choose step 3 banknotes as the entry point for fiat money. But this would be unconventional, since most note-issuing central banks in the 1800s were running this sort of 70%/30% system, and we usually call the monetary system that prevailed in the 1800s a gold standard, not a fiat standard.

4) The central bank announces that it  will undergo extensive renovations. As a result, its redemption window will have to be shut for two months. People can no longer redeem their $1 for 1 gram of gold on demand, but will have to wait until the renovations are over.

Fiat or not? Two months is a long time. But it could be that the central bank already closes its doors on the weekends anyways, banknotes being inconvertible for 48-hours. I doubt many of us would describe the weekend as a fiat currency episode. Should we think of the renovation closure as an extended weekend, or is it long enough that it generates fiat money?

5) Unfortunately the central bank chose an incompetent construction company. Renovations will take another two years!

To make up for the inconvenience of the redemption window being closed for such a long time, the central bank promises to send agents to the local gold market who will ensure that the market rate stays fixed at $1/gram. These agents will buy & sell whatever amount of gold is necessary to maintain the peg (by selling and buying banknotes).

Fiat or not? Thanks to the strategy of buying and selling in the local gold market, the $1/gram price holds just as well as it did in steps 2 and 3. So the public notices no difference in the purchasing power of the money in their wallets. On the other hand, two years without a redemption window at the central bank may be long enough for many readers to tick the fiat money box.    

6) The central bank is still undergoing renovations, but instead of dispatching agents to the market to buy and sell gold to enforce the peg, they go with bonds in hand.

If the market price for gold threatens to rise from $1/gram to $1.01/gram, because there is too much money chasing too few goods, the agents sell bonds and withdraw banknotes, thus reducing pressure on the exchange rate and bringing it back to $1/gram. And when the exchange rate threatens to fall below $1/gram to $0.99/gram, because there is too little money chasing goods, agents buy bonds with banknotes.

Fiat or not? Not only are notes not redeemable in gold, but now the central bank no longer operates directly in the gold market. With this step we are getting a bit closer to modern central bank money. The Federal Reserve, the Bank of Canada, and other major central banks all regulate the purchasing power of money by purchases and sales of bonds. The $1/gram peg still holds thanks to bond purchases and sales, so step 6 money does almost everything that step 2 and 3 money does.

7) With the renovation dragging on, the central bank decides that it doesn't need a redemption window after all. So what was initially a temporary suspension of convertibility becomes permanent. But the central bank continues to send agents to the market to buy or sell whatever quantity of bonds are necessary to maintain the $1/gram peg.

Fiat or not? You tell me. Perhaps permanent inconvertibility is the very definition of fiat. However, if steps 2-6 didn't qualify as fiat money, because gold stayed at $1/gram, why would step 7 be any different?

8) The central bank decides that, rather than fixing the market price of gold at $1/gram, it will set the market price of a typical consumer basket of goods and services (i.e. meat, car repairs, school, etc). 

This is a bit trickier to think about than the other steps. So for example, say that the central bank is currently setting the price of gold at $1/gram. And people can buy a consumer basket for $1000. But the price of that basket starts to rise to $1010, $1020, and then $1030. To stop this inflation, the central bank will announce its intention to reduce the price of gold to $0.99/gram. It does this by selling bonds and withdrawing money from the system, so that there is less money chasing goods. It keeps repeating gold price decreases/money withdrawals until it has successfully reigned in the inflation and brought the consumer price basket back to $1000. The net effect is that consumers are always guaranteed that the money in their pocket has constant purchasing powe

Fiat or not? This is pretty much the monetary system we have now in the U.S. and Canada where central banks target inflation. Well, there are a few small differences. Instead of temporarily setting the price of gold in order to regulate the value of a consumer price basket, the Fed and Bank of Canada temporarily set the price of a very short-term debt instrument to hit their target for the basket. And rather than shooting for constant consumer goods and services prices, these central banks prefer one that shrinks by 2% a year.

Given that step 8 describes something close to modern money, and it is common practice to refer to modern money as fiat, then it would only make sense that many readers raise their hands at this point. Complicating matters is that step 8 money isn't really that different from steps 2 to 7. After all, the central bank is establishing a fixed price for banknotes, the only difference being that the fix has been adjusted from gold to a basket of consumer goods and services. 

9) The central bank donates all of its assets to charity, closes its doors and shuts down for good. But it leaves all its banknotes outstanding. Money floats around the economy without a tether to reality. Or as Stephen Williamson says, money is a bubble.

Fiat or not? By this stage, everyone will probably have ticked the fiat money box. 


Here is a collection of unconnected thoughts on the fiat-or-not game.

A) My guess it that readers will have chosen different stages as their preferred debut for fiat money. This is a bit tragic, since with no commonly-accepted definition for the term, most debates about fiat money have been and will continue to be meaningless.

B) We apply our definitions like cookie cutters to the real world. So if you chose step 7 (when banknotes became permanently irredeemable) as your flipping point, then 1971 would be a very important date in your scheme of the world since this is when the U.S. permanently removed gold convertibility.

But if you chose step 9 as your transition point to fiat, then the global monetary system is not currently on a fiat standard, since central banks have neither closed their doors nor donated their assets to charity. So 1971 really isn't an interesting date. I'm aware of only one country on a step 9 fiat standard: Somalia. Its central bank burned down yet Somali shilling banknotes continued to circulate. And ironically enough, if we choose to adopt a step 9 definition of fiat money, then bitcoin—which was designed to destroy central bank "fiat" money—is itself fiat, because it is unbacked, whereas most central bank money is not fiat.

What I've described is the Borges problem. Categories pre-digest the world for us. We get very different results depending on what definition we use and how we apply it to the world.

C) I think many readers associate fiat with hyperinflatable. For instance, here is Dror Golberg:

Readers who conflate fiat and hyperinflatable will probably have played the fiat-or-not game by gauging each step to see if it introduced (or removed) a set of features perceived to be conducive (inhibitory) to high inflation. They probably toggled the fiat button somewhere in the murk of temporary inconvertibility (step 4) and permanent inconvertibility (step 7). The thinking here is that convertibility into specie imposes a more imposing restriction on a central bank than a mere promise to hold gold's value at $1/gram by using open market operations (step 6). With the removal of convertibility, hyperinflatability is activated and thus money has become fiat.

There are certainly some good historical reasons for assuming that inconvertibility leads to hyperinflatability. Some of the most famous hyperinflations occurred after redemption was removed, including John Law's paper money scheme, the American Greenback episode, and the Wiemar inflation. But there is no inherent reason that these systems must lead to hyperinflation, or that step 1 (coin-based systems) and step 2 (fully convertible) systems aren't themselves hyperinflatable. In the case of coin-based systems, all that it takes is a rapid series of reductions in the silver content of coins to set off inflation, Henry VIII's consistent debasement of the English coinage being one example. And there is no reason that a fully convertible step 2 banknote system can't undergo a series of large devaluations leading to hyperinflation. 

D) Fiatness, fiatish? If we can't agree on what constitutes fiat-or-not, maybe we can agree that there might be a fiat scale, from pure fiat to not fiat at all, with most monetary systems existing somewhere in between. I am already on record advocating moneyness over money, so this fits with the general them of the blog. On the other hand, fiatness seems a bit of a cop-out.

E) We don't need gobbledygook like fiat. The term carries too much baggage. Let's select a more precise set of words, then apply them to the real world in order to understand what our monetary systems were like, how they are now, and where we are going. Until we settle on these words, let's avoid all conversations with the term fiat in them.

P.S. I have a recent post about the desirability of coin debasements at the Sound Money Project and another post on money as a measuring stick at Bullionstar. 

Wednesday, March 21, 2018


I am a big fan of coinsplainers like Andreas Antonopoulos. Listening to Andreas explain how bitcoin works is a great learning opportunity for folks like myself who know far less about the topic. I am less impressed when bitcoiners engage in fiatsplainin', since they generally have an iffy understanding of the actual financial system and central banking in particular.

So for the benefit of not only bitcoiners, but anyone interested in the topic of money, I'm going to fiatsplain' a bit. (I really like this term, I got it from an Elaine Ou blog post)

Paul Krugman recently had this to say about the difference between bitcoin and fiat money:
"So are Bitcoins a superior alternative to $100 bills, allowing you to make secret transactions without lugging around suitcases full of cash? Not really, because they lack one crucial feature: a tether to reality.
Although the modern dollar is a “fiat” currency, not backed by any other asset, like gold, its value is ultimately backed by the fact that the U.S. government will accept it, in fact demands it, in payment for taxes. Its purchasing power is also stabilized by the Federal Reserve, which will reduce the outstanding supply of dollars if inflation runs too high, increase that supply to prevent deflation.
Bitcoin, by contrast, has no intrinsic value at all. Combine that lack of a tether to reality with the very limited extent to which Bitcoin is used for anything, and you have an asset whose price is almost purely speculative, and hence incredibly volatile."
Now if you've been reading my blog for a while, you'll know that I agree with Krugman's point that bitcoin lacks a tether to reality while a banknote doesn't. He mentions two forces that anchor a $100 banknote, or provide it with intrinsic value: tax acceptability and a central bank's guarantee to regulate its quantity. Let's explore each of these anchors separately, starting with tax acceptability.


The idea that taxes can determine the value of a fiat currency is easier to grasp by looking at currencies issued during the American colonial era. Coins tended to be scarce in the 1700s and there were few private banks, so the legislatures of the colonies issued paper money to meet the public's demand for a circulating medium. They had a neat trick for ensuring that this paper money wasn't deemed worthless by citizens. A fixed quantity of paper money was issued concurrently with tax legislation that scheduled a series of future levies large enough to withdraw each of the notes that the legislature had issued. This combination of a fixed quantity of notes and future taxes of the same size was sufficient to give paper money value, since the public would need every bit of paper to satisfy their tax obligations.

Examples of colonial currency (it's worth enlarging this image to see the detail) From: Early Paper Money of America

Crucially, once a colonial government had received a note in payment of taxes, it removed said note from circulation and destroyed it. If the government re-spent notes that had already been used to discharge taxes, this would be problematic. The tax obligation would be more-than-used-up, leaving no reason for the public to demand outstanding banknotes. Krugman's "tether to reality" would have been removed.


The modern day version of Krugman's tax acceptability argument is a bit more complicated. For starters, no one actually pays their taxes with banknotes. Rather, the tax acceptability argument applies to a second instrument issued by central banks otherwise known as reserves (in the U.S.) or settlement balances (in Canada). All commercial banks keep accounts at the central bank, these accounts allowing them to make instant electronic payments to other banks during the course of the business day, or to the government, which typically will also have an account at the central bank.

When Joe or Jane Public are ready to settle their taxes, they initiate a set of financial transactions that ultimately results in their bank depositing funds on their behalf into the government's account at the central bank. To satisfy the public's demand to make tax payment, commercial banks will want to have some central bank settlement balances on hand. So the existence of taxes "drives" banks to hold a certain quantity of central bank settlement balances, thus generating a positive price for these instruments. And since a banknote is in turn tethered to a central bank deposit via the central bank's promise to convert between the two at par, by transitivity the banknote is also tethered.

Unlike the colonial era, however, the tax authority—the government—can't destroy money. The government can either accumulate central bank deposits, or spend them, but it can't cancel them. What generally happens with the government's account at the central bank is that as soon as it is topped up with some tax receipts, they get quickly spent on government programs, salaries, and other expenses. So these funds simply boomerang right back into the accounts that commercial banks keep at the central bank, undoing the tethering that is achieved by tax acceptability.

Put differently, for every bank that demands settlement balances to pay taxes, and thus help gives those balances value, there is a government official who spends them away, and negates this value. So government taxes by themselves don't anchor modern central bank money.

To really anchor the value of central bank money, the government needs to withhold from spending the money it has received from taxes. The more it resists spending incoming tax flows, the more balances accumulate in its account at the central bank. If the government keeps doing this, at some point almost every single deposit that the central bank has ever issued will have been sucked up into the government's account. With almost no deposits remaining for paying taxes—and thus no way for the public to avoid arrest for failure to meet their tax obligations—the value that banks collectively place on deposits will reach incredible heights.

And that explains how tax acceptability (combined with a strategy of not spending taxes received) can provide modern fiat money with backing sufficient to generate a positive price.


Let's turn now to Krugman's second reason for central bank money having intrinsic value, the central bank itself. As I said earlier, a government can freeze deposits by accumulating them, but it can't destroy them. The only entity that can destroy money is the central bank. It achieves this is by conducting open market sales of bonds and other assets. When it sells a bond to a bank, the central bank gets one of its own deposits in return, which it proceeds to destroy.

Imagine that banks collectively decide they have too many central bank deposits and start to sell them (a scenario I discussed here). This sudden urge to rid themselves of money will cause inflation. In a worst case scenario, they will get so desperate that the purchasing power of money falls to zero. The central bank can counter this by selling assets and destroying deposits. In the extreme, it can sell each and every one of the assets it owns, shrinking the deposit base to zero. Its actions will drive the value of deposits into the stratosphere, since banks need a token amount to make interbank payments.

And that, in short, explains how central banks can provide dollars with backing sufficient to generate a positive price.


Which of Krugman's two forces—tax acceptability or a central bank's guarantee to regulate the quantity of money—is more important for imbuing little electronic bits with value?

We know that a government can anchor a fiat money purely through tax acceptability. Colonial money proves it. (Here is another example from the Greenback era) But can a fiat currency be anchored solely through the actions of the central bank, without the help of tax acceptability? Let's set the scene. Imagine that the government has unplugged itself from the central bank by closing its account and instead opening accounts at each of the nation's commercial banks. Since all incoming tax receipts and outgoing government payments are now made using private bank deposits, the government no longer generates a demand for central bank settlement balances.

This "unplugging" needn't drive the value of central bank money to zero. The central bank has assets in its vault, after all, so any decline in the value of central bank money can be easily offset by an appropriate set of central bank open market sales and concomitant reductions in the quantity of deposits. So the answer to my question in the previous paragraph is that money doesn't require tax acceptability to have intrinsic value. Tax acceptability is sufficient, but not necessary.

That being said, on a day-to-day basis the value of modern central bank money is regulated by a messy combination of both factors. Money is constantly flowing in and out of the government's account at the central bank, and this can have an effect on the purchasing power of money. Likewise, central bank open market operations are frequently conducted on a daily basis in order to ensure the system has neither a deficiency nor an excess of balances. It's complicated.

And that ends this episode of fiatsplainin.' Fiat money is indeed backed and has intrinsic value, as Krugman says, and it does so for several reasons.

PS. If you are interested in colonial currency, you should read some of Farley Grubb's papers.


On Twitter, someone had this to say about my post:
฿ryce gives me the perfect opportunity to keep fiatsplainin'. Contrary to ฿ryce's claim, the fact that Arizona plans to accept tax payments in the form of bitcoin does not provide bitcoin with a tether to reality. For every bitcoin that Arizona accepts, it will just as quickly spend it away. The first is undone by the other. You'll notice that this is the same reason I gave for modern central bank money not necessarily being anchored by tax acceptability; whereas taxes vacuum up central bank money, government officials typically reverse this vacuum by quickly spending it, so the net effect is a wash.

To tether central bank money to reality, governments need to not only make it tax acceptable but also  be ready to let those balances pool up in its account, thus setting a limit on the overall supply of balances. Likewise with bitcoin. If the Arizona government were to accumulate incoming bitcoins as part of an overall policy of never spending them, then it would be removing bitcoins from circulation, in essence "destroying" them. And this would provide bitcoin with a true anchor. Of course the Arizona government isn't going to do this. It will want to rid themselves of bitcoins the moment it gets them.

Wednesday, March 7, 2018

Indians' "ill-informed notions" concerning the legitimacy of ₹10 coins

The BBC has an interesting story about India's coinage. Apparently more and more Indians  believe that the ₹10 coin is not real, or that it has been banned by the authorities, and as a result they are unwilling to accept them in trade. Doubts about the ₹10 coin have been emerging for several years now: Amol Agarwal has covered the story here, here, and here.

This is an excerpt from the BBC article:
"Nobody accepts the coins - grocery shops, tea stalls, nobody accepts it", an auto rickshaw driver in the southern state of Tamil Nadu told BBC Tamil.
In the southern city of Hyderabad, a young girl told BBC Telugu she had been saving up to buy her brother a gift but several shop owners wouldn't take her 10 rupee coins.
A man on his way to a job interview was forced to get off the bus because the conductor wouldn't accept 10 rupee coins, the only currency he had.
"They say it's because the other passengers don't accept the coins in return", explains a shop owner who also said bus conductors wouldn't take the coins.
The Reserve Bank of India (RBI) has twice addressed the public's worries about the ₹10 coin. In a 2016 announcement it begged Indians to ignore "ill-informed notions" concerning the legitimacy of ₹10 coins and to continue to "accept these coins as legal tender in all their transactions without any hesitation." More recently, in a January notice, we learn that the RBI has issued fourteen different designs for the ₹10, all of which are "legal tender and can be accepted for transactions."

What are the underlying reasons for Indians' fears? One interesting fact about the ₹10 coin is that it is relatively new, having been introduced back in 2009. People are always skeptical about new monetary instruments, which generally take a long time to acquire trust.

Another interesting fact is that in addition to minting a ₹10 coin, the RBI also prints a ₹10 banknote. The ₹10 banknote has a long history, having debuted before independence in 1947. Below is a chart showing how many of each instrument is in circulation. The year-over-year net increase in banknotes continues to outpace the increase in coins by a large amount, indicating that  Indian's have a preference for the paper version of the ₹10.

I think there is an easy explanation for the ₹10 coin's loss of currency. Because the ₹10 coin and ₹10 note are perfect substitutes, and converting between them incurs no conversion costs, there is no disciplining mechanism to prevent irrational worries about the newer of these two instruments from crippling its usage. Put differently, hating new ₹10 coins doesn't impose any costs on the hater as long as an equivalent banknote can be used. If there was no such thing as the ₹10 banknote, then anyone who refused to use the ₹10 coin would face much higher costs for being unreasonable. After all, holding two ₹5 coins or five ₹2 coins in the place of a ₹10 coin is inconvenient.

The denomination at which a monetary system switches from coins to notes is referred to by Rocheteau and Lotz (pdf) as the coin-note frontier. In Canada, for instance, the frontier lies between the $2 coin and $5 note, while in Switzerland it lies between the 5 franc coin and 10 franc note. Most frontiers (like Canada's and Switzerland's) are staggered—the largest coin is smaller than the smallest note. This staggering makes a lot of sense. Why should both the nation's mint and its printing presses incur the fixed costs of producing the same unit when one will suffice? Consider too the waste incurred in the doubling-up of the tasks of distributing, sorting and handling a coin and note of the same denomination.

Unlike most countries, India has an even coin-note frontier. For some reason, the Indian monetary authorities have decided to have both the mints and the presses replicate the same task of producing the ₹10. Interestingly, India isn't alone. The U.S.'s largest coin is $1 while the smallest note is $1.

The US's $1 coin, introduced in 1979 and referred to as the Susan B. Anthony dollar, is commonly considered to be a major monetary failure. I wrote about it here. $1 coins have proven to be unpopular with the American public, huge amounts of them accumulating in vaults at various Federal Reserve banks. Because the US monetary authorities decided to introduce the $1 coin without removing the $1 bill, the public was given a choice between a perceived "good" currency, the existing and comfortable note, and a "bad" currency, an unfamiliar coin. They took the less costly route and stuck with the "good" notes. My guess is that the very same forces that doomed the $1 coin could end up killing off the ₹10 coin.

The failure of the $1 and ₹10 coins is unfortunate. As Rocheteau and Lotz point out, replacing low denomination notes with coins is a good idea because the the cost of keeping bills in circulation is greater than the cost of servicing coins. While coins are more expensive to produce, they last much longer than bills.

So not only are the US and India doubling up their costs by having both the mint and printing presses produce the same instrument, but at the same time the decision to keep the note in circulation means that the more efficient instrument—the coin—is destined to fail. The Reserve Bank of India blames the public's "ill-informed notions" for the ₹10 coin's loss of currency. But perhaps it should be blaming itself for providing the right conditions that allow for the spread of these ill-informed notions. Remove the ₹10 note and the problem will be fixed.

Amol Agarwal has some comments here.

Friday, March 2, 2018

The odd relationship between gangster and central banker

In my recent post for the Sound Money Project, I touched on the odd relationship between central banker and gangster. I want to focus a bit more on this relationship.

An awkward truth of central banking is that one of the central bank's most important lines of business—the business of providing cash, specifically high denomination banknotes—primarily serves hoodlums, gangsters, tax evaders, and the mafia. Yes, non-criminals certainly make some use of high denomination banknotes, say a few notes hidden in the cookie jar in case the electricity goes down. But the largest base of users is comprised of folks who hold notes—not in cookie jars—but by the suitcase full; criminals. Banknotes are anonymous after all, so they are an excellent way for criminal organizations to make large-scale transactions without being traced.

Providing criminals with high-denomination banknotes is a lucrative line of business. For each $100 note put into circulation, a central bank holds $100 worth of interest earning assets in its vaults. Since note holders don't have the right to receive any interest, the central banks gets to keep all this interest income for itself.

For instance, by the end of 2016 the Bank of Canada had placed $80.5 billion worth of banknotes into circulation. Large denomination banknotes—the $50, $100 and $1000 notes—accounted for $58.4 billion of this, or around 72% of all banknotes. The assets standing behind all outstanding banknotes allowed the Bank of Canada to earn $1.53 billion in interest in 2016. Of this amount, around $1.1 billion (72% of $1.53 billion) can be attributed to high denomination banknotes, the majority of which comes courtesy of the largest holders of high denomination notes: gangsters.

So you can begin to see why the Bank of Canada might not want to get out of the business of producing $50, $100, and $1000 notes. $1.1 billion is a lot of profit! Of course, were the Bank to get out of producing high denomination notes altogether, it wouldn't forgo the entire $1.1 billion in yearly income. Criminals might choose to use $10 and $20 notes in the place of the demonetized high denomination notes. However, $10s and $20s are a bulky way to store value. They surely wouldn't be capable of recapturing all of the criminal wealth formerly held in the form of $50, $100, and $1000 notes. Which means that the total amount of banknotes outstanding would fall and Bank of Canada profits would shrink.

Why might central bankers care about their profits? As I wrote here, any government bureaucrat who can provide their master with an ongoing revenue stream will always have more say in their department's fate than a bureaucrat who has to ask for funding each year. And of all government bureaucrats, none is more jealous of their independence than the central banker. The process of ratcheting the interest rate lever higher or lower requires a complete absence of political meddling, so say central bankers. One might imagine that this autonomy is worth so much to central bankers that it justifies taking on a clientele dominated by gangsters.

There is a better reason for why it might be in the public interest for central bankers to continue serving criminals with high denomination banknotes. Consider the fact that if high denomination notes were to be rescinded, criminals would simply use other forms of payment in their place. If the substitute payments medium that criminals select places a new and extremely onerous set of burdens on society, then maybe the public provision of high denomination notes should not be discontinued.

What alternative payments media might criminals use in the place of $100 and $50 notes? In his screed against high denomination banknotes, Ken Rogoff suggests that gold, uncut diamonds, and bitcoin might become popular as a criminal payments media. The fact that these instruments are cumbersome relative to cash would make criminals easier to catch, and Rogoff claims that the crime rate might even drop.

In a provocative article, James McAndrews counters that rather than turning to commodities, criminals will instead select private debts as their preferred payments medium. A thief who sells stolen goods to a fence would accept some sort of IOU as payment rather than cash or diamonds. This IOU wouldn't be anonymous. Like any debt, the debtor and creditor would be a matter of record. But as long as the system of debts is secret—i.e. only criminal participants can see the record—then the users can't be tracked by the authorities, like cash.

When an IOU defaults, the traditional legal system provides a means for sorting things out. But this system would be out of bounds to criminals trafficking in IOUs. What is required is some sort of underground administrator or third-party to act as arbiter. According to McAndrews, the party that is likely to emerge as enforcer of criminal debts is organized crime: the mafia. 

In addition to enforcing IOUs, the mafia would also be in a position to fabricate new IOUs for use in the criminal monetary system. McAndrews uses the example of inflated invoices. The mafia would coerce legitimate businesses into writing IOUs, or invoices, for goods they never bought, or bought  at inflated prices. These invoices would circulate among criminals as money. To assure that the police ignored their extortion of legitimate business, the mafia would resort to stepped up bribery of the police.

All of this changes the calculus of a central bank withdrawal from the business of providing criminals with banknotes. Sure, a demonetization of high denomination notes might lead some gangsters to go legit because the lack of $100 and $50 notes makes their business too expensive to operate. But a whole new range of crimes could emerge. Violence could grow as the mafia executes defaulters in order to maintain the sanctity of the new IOU payments system that has taken the place of high denomination banknotes. Legitimate businesses could get blackmailed into feeding the criminal monetary system, those run by immigrants likely being the most vulnerable. And police departments will be corrupted.

McAndrews uses the public provision of free condoms and clean needles as an analogy. Restrict free condoms and it is possible that the rate of sexual intercourse goes down. But surely there will be an increase in unsafe sex, unplanned pregnancy, and sexually transmitted diseases. As for the provision of clean needles, restrict it and heroin use might fall. However, the prevalence of HIV will rise. Both unsafe sex and dirty needle usage impose costs not only on those directly afflicted but also indirectly on us—i.e. taxpayers who pay increased health care expenditures.

Likewise with cash. A restriction of $50 and $100 notes could very well lead to attrition in the ranks of existing criminals, as Ken Rogoff reasons. However, this could be twinned with an increase in mafia activity and the potential subordination of us—i.e. legitimate business—to the needs of the underground payments system. Keeping high value banknotes may thus be the wise decision, in the same way that choosing to keep free condom and clean needle programs going makes everyone's lives better off.