Causes of Inflation, and Which Kind Hurts You

Inflation has several distinct drivers, and which one is operating determines whether your income rises with your costs or falls behind them. The primary causes:

Supply of Money

When the central bank creates money faster than the economy creates goods, prices eventually rise — more dollars chasing the same output. The Federal Reserve does exactly this in every recession: cut rates, buy assets, expand the money supply. Cheap money lifts spending, corporate profits, and asset prices first; consumer prices move later, if at all — and the “if” is the interesting part.

The relationship is captured by the equation of exchange, $\mathit{MV}=\mathit{PQ}$: the money supply $M$ times its velocity $V$ (how many times each dollar changes hands in a year) equals the price level $P$ times real output $Q$. Rearranged into rates of change, it gives the inflation identity:

$$\pi \approx \%\mathrm{\Delta }M+\%\mathrm{\Delta }V-\%\mathrm{\Delta }Q$$

where $\%\mathrm{\Delta }$ reads “the percentage change in.” Velocity is the term everyone forgets, and forgetting it is why so many confident predictions fail. The Federal Reserve expanded its balance sheet enormously after 2008 and consumer inflation stayed below target for a decade — because velocity collapsed at roughly the rate money was created, and the new reserves sat in the banking system rather than chasing goods. The same expansion in 2020–2021, arriving with direct transfers to households and constrained supply, produced a very different result. Money growth is a necessary ingredient, not a sufficient one.

The increase in money supply is often a feature, not a bug, of a credit-based money system. Over the years, growth of the economy as reflected in stock prices has exceeded consumer price inflation — which is the single strongest argument for owning productive assets rather than currency.

Demand-Pull Inflation

Aggregate demand outpaces aggregate supply — too much money chasing too few goods. Driven by consumer spending, government expenditure, or investment. This is the benign variety, in the sense that it arrives alongside a strong labor market: your costs rise, but so does your bargaining power over your own wage.

Cost-Push Inflation

Production costs rise — energy, raw materials, wages, tariffs — and producers pass them through. This is the dangerous variety for a household, because your costs rise without the tight labor market that would let you demand more income. An oil shock makes everyone poorer at once; that is why it tends to arrive with a recession attached.

Built-In Inflation

Workers demand higher wages to keep pace with prices, employers pass the labor cost through to prices, and the cycle feeds itself — the wage-price spiral. This is why central bankers care so much about expectations: once households and firms start assuming 5% inflation and pricing it into contracts, the assumption becomes self-fulfilling and takes a recession to break.

Exchange Rate Inflation

A depreciating currency makes imports more expensive. Modest for a large, relatively closed economy like the United States; severe for import-dependent economies, and one reason emerging-market currency crises turn into inflation crises so quickly.

Fiscal Policy

Deficit spending and tax cuts add demand. Whether that produces inflation depends on whether the economy has slack: the same stimulus is absorbed by idle capacity in a recession and shows up in prices at full employment.

Knowing the mechanisms is useful for understanding what you are reading, not for trading on it. The causes above are diagnosed confidently in hindsight and argued about endlessly in the present, and by the time a driver is obvious enough for you to act on, it is in the price (section “Forecasting: What the Market Already Thinks”). What the taxonomy is genuinely good for is recognizing which kind of inflation you are in, because the varieties are not equally survivable: demand-pull inflation accompanies a strong economy and rising wages, while cost-push inflation arriving from an energy or supply shock raises your costs without raising your income. The second kind is the one that damages a household balance sheet, and the defense against it is structural — fixed-rate debt, productive assets, and income that reprices — not a tactical rotation into commodities after the shock has already happened.