Inflation is the rate at which the general level of prices rises. Its effect on a portfolio is easy to overlook because it never appears on a statement.
Nominal and real
A nominal return is the change in the account balance. A real return is that change after inflation — the change in what the money can buy.
The relationship is approximate but useful: real return ≈ nominal return − inflation. If a portfolio returns 5% in a year when prices rise 4%, roughly 1% of purchasing power was gained.
Over long periods, the gap dominates. Twenty years of a 5% nominal return with 4% inflation leaves real capital almost unchanged, while a 5% nominal return with 2% inflation roughly doubles it. The investor in both cases sees the same statement.
What inflation changes
Different assets respond differently, and not reliably in the same direction:
- Cash loses purchasing power at approximately the inflation rate. It is the asset most obviously exposed.
- Fixed-income suffers twice: rising inflation usually pushes interest rates up, which lowers bond prices, and the fixed coupons buy less.
- Equities can pass through price increases, but not always and not immediately. Pricing power is the relevant quality — a company able to raise prices without losing customers is better protected than one that cannot.
- Commodities tend to move with inflation, since they are the input prices being measured, but they produce no income and can be extremely volatile.
- Real assets and inflation-linked bonds are explicitly structured around price indices.
Why it matters for allocation
Inflation is the reason a portfolio cannot be built from the safest nominal instruments alone. A holding that cannot lose nominal value can still lose real value, and over a long horizon the second loss is the larger risk.
It also explains why the stated objective matters. "Preserve capital" and "preserve purchasing power" are different instructions that lead to different portfolios.
What to watch
Rather than a single number, the useful observations are:
- Whether inflation is demand-driven or supply-driven. Central banks can address the first more directly than the second.
- Whether expectations are becoming unanchored — that is, whether people begin behaving as though inflation will persist.
- The gap between headline and core measures, which differ by whether volatile food and energy prices are included.
A note on precision
Inflation is measured by indices that describe an average basket. Any individual's experience differs, depending on what they spend on. The number is a useful approximation of a general trend, not a personal cost-of-living figure.