Foundations
How inflation quietly shrinks a savings account
Nothing about inflation looks like a loss. No money leaves, no statement shows a minus, and the balance goes up every year. What falls is the only thing that was ever the point, which is what the balance can buy.
Inflation is the general tendency of prices to rise, which means it is also the general tendency of a fixed amount of money to buy less. Those are the same sentence viewed from two ends, and the second version is the one worth internalising, because it is the one that describes what happens to your savings.
The mechanism, in one paragraph
You hold 10,000. Prices rise 3 percent over the year. Your 10,000 is still 10,000, but the basket of things it would have bought now costs 10,300. You did not lose money. You lost purchasing power, and no statement anywhere records that event. It is a loss with no transaction attached, which is exactly why it is so easy to ignore for a decade at a time.
What makes it serious rather than annoying is that prices compound. Each year the rise applies to the already risen level, in exactly the same way that compound growth works in your favour on the other side of the ledger. The same arithmetic, pointed the other way.
What 10,000 buys, later
| Prices rise by | After 5 years | After 10 years | After 20 years |
|---|---|---|---|
| 2% a year | $9,057 | $8,203 | $6,730 |
| 3% a year | $8,626 | $7,441 | $5,537 |
| 4% a year | $8,219 | $6,756 | $4,564 |
Read the bottom right cell slowly. At 4 percent a year, twenty years of holding cash under a mattress leaves you with the buying power of about 4,564 out of an unchanged 10,000. Nobody stole anything. The number on the account never moved.
Two percentage points of difference between the top row and the bottom row, over twenty years, is the difference between keeping two thirds of your purchasing power and keeping under half of it. Which is why the gap between an interest rate and an inflation rate deserves far more attention than either number on its own.
Nominal and real, and why only one matters
Two words do most of the work here, and they are worth using precisely.
- Nominal return
- The figure on the statement. What the balance did, in currency terms, before any adjustment.
- Real return
- The nominal return with inflation removed. Roughly, the difference between the two rates. This is the number that tells you whether you are actually better off.
Ten thousand at 2 percent, while prices rise 3 percent
- Balance after 10 years $12,190
- What that balance buys, in today terms $9,070
- Real change over the decade -$930
Arithmetic at fixed rates, compounded annually, not a forecast. The account paid interest every year and the saver still ended the decade able to buy about 9 percent less than at the start. A positive nominal return and a negative real return at the same time is an ordinary situation, not an exotic one.
The rule of 72, run backwards
The same shortcut used for growth works on prices. Divide 72 by the inflation rate to estimate how many years it takes for prices to double, which is also how long it takes for money to halve in purchasing power.
- At 2 percent, prices double in roughly 36 years.
- At 3 percent, roughly 24 years.
- At 6 percent, roughly 12 years.
Check it against the arithmetic: a basket costing 100 today, with prices rising 3 percent a year, costs about 203 after 24 years. The shortcut is close enough to do in your head, and it converts an abstract percentage into a span of a working life.
Why the buffer stays in cash anyway
Everything above is an argument against holding long term money in cash. It is not an argument against holding a cash buffer, and conflating the two leads people to invest money they need next month.
An emergency fund is bought for certainty, not for growth. Losing a small amount of purchasing power each year is the premium you pay for the guarantee that the amount will be there, in full, on a day nobody warned you about. Judging that pot by its real return is like judging a spare tyre by its fuel economy.
That separation is the whole subject of saving and investing are two different jobs, and inflation is the reason the second job exists at all.
What inflation does to debt and wages
Savings are only one of the three places inflation shows up in a household, and the other two are worth naming because they point in different directions.
Fixed rate debt gets easier. If you owe a fixed amount and prices and wages generally rise, the real weight of that debt falls over time. You repay in money that is worth less than the money you borrowed. This is a genuine and underappreciated effect, and it applies only to debt whose rate is actually fixed.
Wages are the real test. Inflation only reduces your standard of living if your income does not keep pace with it. A 3 percent rise in a year when prices rose 4 percent is a pay cut written as a raise, and it is worth doing that subtraction rather than reacting to the headline figure.
Your own inflation rate is not the published one. A published figure is an average across a representative basket. If a large share of your spending sits in a category rising faster than average, your personal rate is higher than the number in the news. That is another reason to know what your own month actually contains, which is the job of a spending record.
Common questions
Does a high interest savings account solve this?
It narrows the gap and rarely closes it, because the rate on a highly liquid account and the rate of price rises tend to move together with the second usually ahead. The account is still the right place for short term money; it is simply not a growth strategy.
Is inflation always bad for an investor?
It is bad for anything paying a fixed amount, which is why it matters so much for bonds. Companies that can raise their own prices are affected differently, though not reliably or evenly, and nobody should treat that as a guarantee.
Should I hold less cash because of inflation?
The buffer is sized by months of essential spending, not by the inflation rate. What inflation argues against is holding cash far beyond the buffer for money you will not need for a decade.
Why do the figures in this guide use round rates?
Because they are illustrations of a mechanism rather than predictions. Using a precise published figure would suggest a forecast, and no rate on this page should be read as one.
Every figure here is arithmetic worked at a fixed, stated rate to show how purchasing power behaves. None of it forecasts inflation, interest rates or returns, and none of it is a recommendation about where to hold money.