Cumulative inflation: why prices do not go back down when it falls

Short answer: when inflation falls, prices keep rising, only more slowly. Inflation measures the pace of the increase, not the level of prices. That is why, after a few years of increases, the cost of living is higher and rarely goes back to the old level.

Rate and level are not the same

The inflation rate says how much prices rose in a period. The price level is where they are today. A lower rate means the level rises more slowly, not that it goes down. A general fall in prices has another name, deflation, and it is much less common.

The cumulative effect

Increases add up on top of what has already risen. Inflation of 5% a year, repeated for three years, results in a total increase of a little over 15%, because each percentage applies to a price that is already higher.

An example

An item costs R$ 100. With 6% inflation in the first year, it goes to R$ 106. In the second year inflation falls to 3%, and the price goes to R$ 109.18. Inflation was cut in half, but the price kept rising. This is an illustrative example.

Nuances

• Not all prices rise equally: some rise more, others less, and some even fall.
• Your personal sense depends on what you consume most, such as food, rent or transport.
• If income does not keep up with the accumulation, purchasing power shrinks.

Why this matters

Understanding the difference avoids the frustration of seeing "inflation drop" and still feeling that money stretches less. It also helps when negotiating wages and contracts by looking at the accumulated figure for the period, not just the latest number published.

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