Economics & Markets · definition
Inflation
Inflation is a sustained rise in the general level of prices, which means each unit of currency buys less over time. It is usually measured with a consumer price index.
Inflation is a broad, sustained increase in prices across an economy. When inflation runs at 5% a year, the basket of goods that cost $100 last year costs about $105 now; equivalently, each unit of money buys less. Statistical agencies measure it by pricing a representative basket month after month, producing indexes such as the Consumer Price Index (CPI).
Inflation is the quietest force in finance: it never shows up on an account statement, yet over decades it decides what savings, wages and fixed payments are actually worth.
Key takeaways
- Inflation is the percentage change in a price index over time; "core" variants strip food and energy to show the trend.
- Most major central banks target about 2% per year, deliberately above zero.
- Inflation compounds like interest, halving purchasing power roughly every 24 years at 3%.
- The damage lands unevenly: cash and fixed payments lose, debtors with fixed-rate debts effectively gain.
- Hyperinflations and deflations bracket the spectrum, and history supplies brutal examples of both.
How the number is made
Agencies like the US Bureau of Labor Statistics and Eurostat price tens of thousands of items, weighted by what households actually spend: rent, food, energy, services, the lot. The headline figure is the year-over-year change of that index. Three honest complications live inside it. Quality change: when a phone gets better at the same price, statisticians count some of that as a price fall. Substitution: people switch from beef to chicken when beef jumps, and methods differ on how to reflect that. And no single basket fits anyone exactly: a renting student and a home-owning retiree live in different personal inflations. The US adds a wrinkle: the Federal Reserve prefers the PCE index, which usually runs a few tenths below CPI, so "inflation" in American policy debates depends on which series is on screen.
Interactive · see the maths
What inflation does to purchasing power
An illustration of constant inflation, not a forecast or advice. Pick an amount, a yearly inflation rate and a period.
$1,000 today buys what $554 will buy in 20 years at 3% inflation. At this rate, purchasing power halves roughly every 23 years.
Formula: real value = amount ÷ (1 + inflation)years. Actual inflation varies from year to year and differs per household; this tool only illustrates the arithmetic of a constant rate.
Where inflation comes from
Economists group causes in three families. Demand-pull: total spending outruns the economy's capacity (post-pandemic reopening). Cost-push: input costs jump and pass through (the 1970s oil shocks; 2022's energy spike after the invasion of Ukraine). Monetary: money supply growing persistently faster than output. Expectations bind the families together: once households and firms expect inflation, they set wages and prices accordingly, which makes it self-fulfilling, and breaking that loop is expensive. The textbook case is the Volcker disinflation: US CPI peaked at 14.8% in 1980, the Fed pushed policy rates near 19-20%, and the price of credibility was the deep 1981-82 recession.
A century's worth of extremes
| Episode | Where/when | What happened |
|---|---|---|
| Weimar hyperinflation | Germany, 1923 | Prices doubled in days; currency reform required |
| The worst ever | Hungary, 1946 | Prices doubled roughly every 15 hours |
| Oil-shock stagflation | US/Europe, 1970s | Double-digit inflation with stagnant growth |
| Modern hyperinflation | Zimbabwe 2008, Venezuela 2018 | Currency abandonment, dollarisation |
| The deflation trap | Japan, 1990s-2010s | Falling prices, postponed spending, zero rates |
| Post-pandemic surge | Global, 2021-2023 | US CPI peaked 9.1% (June 2022), euro area 10.6%, NL above 14% in autumn 2022 |
The table is the unique value of looking back: inflation is neither a permanent emergency nor a solved problem, and the 2021-2023 episode ended a generation's assumption that 2% was automatic.
Why a little is the target
Central banks aim near 2% rather than 0% for three stated reasons: a buffer against deflation (falling prices make debts heavier and reward waiting, Japan's trap), room to cut real rates in recessions, and measurement bias that overstates true inflation slightly. The target's power is in anchoring expectations; the 2021-2023 surge tested those anchors harder than anything since the 1980s, and the rate-hiking response, described under interest rate, followed the classic script.
Inflation and investments, descriptively
Cash loses purchasing power at exactly the inflation rate; that is the arithmetic in the visualiser above. Fixed bond coupons lose in real terms, which inflation-linked bonds (TIPS) were designed to repair. Equities are a mixed story: businesses can raise prices, but inflationary periods historically brought valuation pressure first (the 1970s were poor for stocks in real terms). Real assets and commodities often track inflation better over long spans, with violent interim swings. None of this ranks anything; it describes the exposures that the word "real return" was invented to compare, alongside compound interest.
Frequently asked questions
Why does the supermarket feel more expensive than the official number?
Frequent purchases (food, fuel) are noticed; falling or stable prices (electronics, subscriptions) are not. Personal baskets also differ from the average, and rent versus ownership treatment varies by index.
Is deflation good, since prices fall?
Mild, productivity-driven price falls can be benign. Broad deflation is historically dangerous: debts grow in real terms and spending is postponed, which is why central banks fear it more than moderate inflation.
What is stagflation?
Inflation plus stagnant growth and high unemployment, the 1970s combination that standard policy struggles with: fighting one half worsens the other.
Sources
This entry is for education only. Investing Value describes how financial concepts work; it does not provide investment, tax or legal advice, and nothing here is a recommendation to buy or sell any asset.