The Quantity — The Level, Plate i

The Money showed what money is — the measure of value, the medium by which all exchange is reckoned. This volume asks a different question: what is money worth, and why does its worth change across time? The value of money is simply what a unit of it will buy, and that is the inverse of the price level: when prices rise, each dollar buys less, so money is worth less; when prices fall, money is worth more. The value of money over time is therefore the story of the price level over time — the story of inflation and deflation. And the oldest and most fundamental answer to what governs the price level is the quantity theory of money, stated with unmatched clarity by David Hume in 1752. The volume opens with it, for everything that follows is a refinement or a complication of its central truth.

The quantity theory holds that the price level is governed by the quantity of money relative to the quantity of goods. Picture the whole economy as a single marketplace, in which a stock of goods is exchanged against a stock of money; the price level is, roughly, the ratio between them — so much money set against so many goods. Now let the quantity of money double while the goods stay the same. There is twice as much money chasing the same output; each good comes to fetch twice as many of the now-more-plentiful dollars; and the price level doubles. The formal statement is the equation of exchange: the quantity of money, multiplied by the speed at which it circulates, equals the price level multiplied by the volume of goods transacted. Hold the circulation speed and the volume of goods roughly fixed, and the price level moves in proportion to the quantity of money. Money's worth, in this view, is governed by its abundance: the more money there is relative to goods, the less each unit of it is worth.¹

1. The quantity theory: the price level is governed by the quantity of money relative to goods. Picture the economy as one marketplace where a stock of goods is exchanged for a stock of money; the price level is roughly their ratio. Double the money against the same goods, and prices double. The equation of exchange: money times its velocity equals the price level times the volume of goods. Hold velocity and output fixed, and the price level moves with the quantity of money. Money's worth is set by its abundance.

Hume drew the radical conclusion that gives the theory its depth: in the long run, the quantity of money affects only prices, not the real wealth of a nation. His thought experiment is the cleanest in economics. Suppose that overnight, silently, every coin in the kingdom were doubled. Would the nation wake richer? It would not. There would be twice the money, but the same fields and workshops, the same goods and skills; prices would simply double, wages would double, and every debt fixed in money would keep its real size, so that every real ratio in the economy stood exactly as before. Money is, in this sense, a veil over the real economy: it sets the level at which prices are quoted, but it does not, in the long run, alter how much is produced or who commands how much in real terms. A nation is no wealthier for holding more money than a country is taller for measuring its hills in feet rather than meters. The quantity of money sets the price level; it does not set prosperity.²

2. Hume's conclusion: in the long run, money's quantity affects only prices, not real wealth — the neutrality of money. His thought experiment: double every coin overnight, and no one wakes richer; prices and wages double, debts keep their real size, every real ratio stands as before. Money is a veil over the real economy — it sets the level prices are quoted at, not how much is produced. A nation is no richer for more money than a country is taller for measuring hills in feet. Quantity sets the price level, not prosperity.

⁂

From the quantity theory follows the central fact about inflation. A sustained, ongoing rise in the general price level is not caused by grasping merchants, or by powerful unions, or by any single price rising — these can raise one price relative to others, a matter of proportion, but they cannot lift every price together, year after year. A general and sustained rise in all prices at once requires a sustained increase in the quantity of money relative to goods. When the money supply grows faster than the economy's output — when an ever-larger stock of money chases a slower-growing pile of goods — the price level rises persistently, and that persistent rise is inflation. The historical record is emphatic: every large and sustained inflation in history has come with a rapid growth in the quantity of money, and there has never been a lasting inflation without one. Inflation, in this fundamental sense, is a monetary phenomenon — too much money, growing faster than the goods it can buy. Particular shocks may jolt prices for a time, but only money, expanded without limit, can sustain a rise without end.³

3. So inflation is fundamentally monetary. A single price can rise relative to others, but no merchant or union can lift every price together for years; that requires the money supply growing faster than goods. When ever-more money chases slower-growing output, the price level rises persistently — inflation. Every large sustained inflation in history came with rapid money growth, and none without it. Inflation, at bottom, is too much money. Shocks jolt prices for a time, but only money expanded without limit sustains a rise without end.

The theory holds in the long run; the short run is messier, and the difference is the key to everything that follows. When new money enters an economy, prices do not all leap at once. The money arrives somewhere first — in the hands of whoever receives it earliest, the borrower, the government, the bank — and these first holders spend it before prices have risen, capturing real goods at the old prices. Those who receive the new money last — often the holders of cash and the earners of fixed incomes, who are frequently the poor — meet the higher prices before their own incomes have caught up. So in the short run money is not neutral at all: changing its quantity quickens or slows real activity, redistributes real wealth from the late receivers to the early ones, and moves output and employment, as the cycle showed. Hume saw this himself — that an increase in money, in the interval before it raises prices, can stir industry into life. The neutrality is a proposition about the long run; the short-run non-neutrality is the source of money's power over real things, and the reason a central bank can do both harm and good.⁴

4. The theory holds in the long run; the short run is messier. New money arrives somewhere first — the borrower, the government, the bank — who spend it before prices rise, capturing real goods at old prices; those who get it last (holders of cash, fixed incomes, often the poor) meet higher prices before their incomes catch up. So in the short run money is not neutral: it quickens activity, redistributes wealth from late receivers to early ones, moves output and employment. Hume saw it. Short-run non-neutrality is the source of money's power — and a central bank's capacity for harm and good.

So the quantity theory lays the foundation for the whole question of money's value. What a unit of money is worth, across time, is governed in the long run by the quantity of money relative to goods: inflation is the fall in money's worth when money grows too fast, and deflation the rise in its worth when money grows too slowly or goods too fast. And since, in the modern world, the quantity of money is governed by a central bank, the value of money is, in the long run, a matter of policy — for the bank, by setting how much money there is, sets the price level, and so sets the worth of every unit of the currency. This is the thread the volume now follows: from the quantity theory, that money's value tracks its abundance, to the tempting question of whether a little inflation might buy lower unemployment; to the catastrophe of money created without limit; and at last to the deepest question, of who should hold a power so great as to move the value of every price at once. The next plate asks whether inflation can be traded for jobs — the Phillips curve, and its undoing.⁵

5. The foundation: money's value over time is governed, in the long run, by the quantity of money relative to goods — inflation when money grows too fast, deflation when too slowly. And since a central bank now sets the quantity of money, money's value is, in the long run, a matter of policy: the bank sets the price level, and so the worth of the currency. The thread: from the quantity theory to whether inflation buys jobs, to money created without limit, to who should hold the power. Next: the tradeoff.

The quantity theory is the foundation of the value of money. The price level — and so money's worth, which is its inverse — is governed, in the long run, by the quantity of money relative to the quantity of goods; double the money and prices double, leaving real wealth untouched, for money is a veil, a counter whose worth is set by its abundance. Sustained inflation is therefore, at its root, a monetary phenomenon: money growing faster than the goods it can buy. In the short run the veil lifts, and money moves real things — quickening industry, shifting wealth from those who get the new money last to those who get it first — which is the source of its power and its peril. And because the quantity of money is now a central bank's to set, the value of money is, in the end, a matter of deliberate choice. The next plate is the tradeoff.