What Money Actually Is

Money does three jobs, and the useful thing about the list is that they come apart.

It is a medium of exchange: the thing you hand over. It is a unit of account: the thing prices are quoted in. It is a store of value: the thing you can hold and spend later. Most of the time one object does all three and the distinction seems pedantic, but in every monetary crisis the functions fail in sequence, and noticing which one is going is the fastest route to understanding what is happening.

The first job is the one the textbooks build the story around, and the problem it solves is real. Under pure barter, a trade requires a double coincidence of wants: I have wheat and want shoes, and I must find someone with shoes who wants wheat, at the same moment, in quantities that divide sensibly. The search cost is enormous, and it scales badly. Money splits every trade into two halves (sell to one person, buy from another) and in doing so makes an extended division of labour possible at all. A society where every exchange requires a matching pair of wants cannot have specialists.

So far, standard. The trouble is with the history that usually accompanies it.

The textbook account, going back to Adam Smith, runs: first there was barter, then people noticed the inconvenience and converged on a commodity everyone would accept, then that commodity was standardised into coin, then coin was replaced by claims on coin, then the claims were cut loose. It is a tidy story in which money emerges from trade as a labour-saving device.

Anthropologists have been pointing out since at least Caroline Humphrey's work in 1985 that no society has ever been found doing the first step. Barter of the kind described, a community running its internal exchange by swapping goods, is not documented anywhere. What is documented, over and over, is credit: people took what they needed and a record was kept, in memory in small communities and on tablets in large ones, with periodic settling. Barter appears mainly between strangers with no expectation of a continuing relationship, or in places where an existing currency has collapsed. It is what people fall back on, not what they start with.

David Graeber's Debt made the argument widely known and pushed it further: if credit came first, then money is best understood as a way of denominating and transferring obligations, and coinage arrives comparatively late and is closely tied to states, armies and taxation (a state that must supply a standing army with provisions from a population it cannot easily bill can issue coins to the soldiers and demand the same coins back in tax, thereby obliging everyone to acquire them).

Not every economist accepts the full thesis, and the historical record is thin enough to support argument. But the negative claim is now fairly settled: the barter origin story is a plausible-sounding reconstruction rather than something anybody observed, and it has been taught as history for two centuries.

Which matters, because the same intuition distorts how people think about money now. If money is fundamentally a commodity that trade converged on, then bank deposits are claims on something, and banks lend out the money that has been deposited with them.

That is not how it works. The Bank of England said so explicitly in a 2014 bulletin, largely because the textbook description had the causation backwards. When a bank makes a loan, it does not move existing money from a saver to a borrower. It writes two entries: a loan on one side, and a new deposit in the borrower's account on the other. The deposit is new money, created at the moment of lending, and it is extinguished when the loan is repaid. The overwhelming majority of what circulates as money in a modern economy came into existence this way, as somebody's debt to a commercial bank.

Central banks influence how much of this happens, through the price of reserves and through capital and liquidity regulation, but they do not do the creating and they cannot simply set the quantity. Which is why the phrase "printing money" describes almost nothing that actually occurs.

The last piece is the one that makes monetary policy stranger than it looks, and it belongs to the unit of account. Wage agreements and price lists are set in advance, against an expected rate of inflation. If everyone expects five per cent, five per cent gets written into next year's contracts, and it then happens, not because anyone caused it, but because everyone priced for it. Expectations are partly self-fulfilling.

This is why central banks talk so much, and why credibility is treated as an asset on a par with any instrument they hold. A bank that is believed can shift behaviour by announcing an intention. A bank that is not believed has to demonstrate its seriousness by causing a recession, which is what the early 1980s were.

And it explains the sequence in a currency collapse. People stop reckoning in a currency first, quoting prices in dollars while still handing over local notes, because a unit that moves hourly is useless for comparison. They stop saving in it around the same time. They go on accepting it in transactions longest, because a note you can spend within the hour still functions. Unit of account, then store of value, then finally medium of exchange. By the time people refuse the notes, the money has already been dead for a while in the ways that matter.