Inflation does not affect everyone at the same rate

Treat the sections below as a sequence. With inflation, getting the early decisions right makes the later ones much easier.

The index is an average of a basket

National statistics offices construct a basket of goods and services weighted by typical household spending, and track its price. The weights are revised periodically, and they represent an average household that does not exist in particular. Your experienced inflation depends on how your spending differs from those weights.

Somebody who spends a large share on energy and food in a year when both rise sharply experiences far more than the headline.

Essentials inflate differently

Food, energy and housing costs are less substitutable than discretionary spending, so price rises there cannot be avoided by trading down. This is why periods of high energy and food inflation hit lower-income households considerably harder than the headline number suggests.

On the balance sheet, several statistics agencies now publish inflation broken down by income decile precisely because the average conceals this. Indices also adjust for quality and for changed pack sizes, so a product that shrinks at the same price can register as a smaller rise than the shopper experiences, and the substitution the method assumes is not open to every household.

Real returns are the only ones that matter

A nominal return of five per cent with inflation at four per cent is a real return of roughly one. Long-horizon planning done in nominal terms consistently overstates what a pot will buy. Working in real terms — today's money — makes retirement and savings projections far more honest and slightly depressing.

Tax, where it applies, is generally charged on the nominal gain rather than the real one, so a high-inflation period can produce a bill on a return that lost purchasing power — a quirk worth raising with a qualified tax adviser in your own jurisdiction.

What protects against it, partially

Assets whose cashflows rise with prices — equities over long periods, index-linked bonds, some property — offer partial protection. Cash offers none, which is why large long-term cash holdings lose purchasing power with certainty. No asset protects reliably over short periods, and anything marketed as an inflation hedge deserves a look at its actual record.

Index-linked bonds track the published index rather than your own basket, and their prices still move with real interest rates, so they can fall in value during exactly the inflationary stretch they were bought to cover.

Debt behaves differently

Inflation erodes the real value of fixed-rate debt, which benefits borrowers at the expense of lenders. That effect is offset where interest rates rise in response and the debt is not fixed. Understanding which of your commitments are fixed in nominal terms clarifies which way inflation moves your position.

On the balance sheet, some liabilities move the other way instead, because rents, student loan balances in certain countries and any repayment terms tied to an index rise with prices rather than being worn away by them.

This is general information, not advice about your particular position.

Incomes are indexed late, and thresholds often not at all

Where pay scales, pensions or benefits are uprated by reference to a past inflation reading, the increase arrives after the prices did and is calculated against the wrong period. That lag is a genuine reduction in purchasing power for the months in between, and it repeats every year the mechanism is used rather than correcting itself. Some countries index automatically and others do it at political discretion, so how much protection a fixed income actually carries is worth checking rather than assuming.

Practically, thresholds left unchanged in nominal terms — tax bands, allowances, benefit limits in some systems — tighten quietly as wages rise, which is a separate squeeze from the one prices apply.

The takeaway

Plan in today's money. The headline rate is an average of a household that is not yours.

Write the number down before you decide. It usually decides for you.