An inflation adjustment is decided once and felt for decades

Retirement income can be arranged to stay level or to rise with prices. The choice is made at the outset, and its effects accumulate across the whole of a retirement.

The two paths cross late

A level income starts higher. A rising one starts lower and increases, eventually overtaking the level payment and then continuing to pull away.

The crossover typically arrives well into retirement. Before it, the level arrangement has paid more in total; after it, the position steadily reverses.

Which is better therefore depends on how long payments continue, which is precisely the thing nobody knows when the choice is made.

Erosion is invisible year to year

A level income loses purchasing power gradually. In any single year the loss is small enough not to be noticed as a change in what the money buys.

Across two or three decades the accumulation is substantial. The same payment supports a materially different standard of living at the end than at the start.

Because the change is slow, it is usually attributed to costs rising rather than to the income having been fixed, which are two descriptions of one thing.

The choice is made at the wrong moment

The decision is taken at the start of retirement, when the immediate difference in payment is vivid and the eventual difference is entirely hypothetical.

A higher starting income is also more useful in the early years, when spending on travel and activity tends to be greatest, which strengthens the immediate case.

That combination reliably pushes people towards level payments, and the reasoning is comprehensible rather than careless. The costs simply arrive much later.

Partial protection exists

Some arrangements increase by a fixed percentage each year rather than tracking a published measure, which provides some protection at a lower initial cost.

Fixed increases are not the same as linked increases. They protect against a particular assumed rate and provide less if prices rise faster than assumed.

Availability of each option, and how any linked measure is defined, differs by provider and jurisdiction and changes over time.

Other income sources are part of the answer

Where a substantial share of retirement income already rises with prices, the case for paying for further protection on the remainder weakens.

Where all other income is fixed, the exposure is concentrated, and the whole household budget is subject to the same slow erosion.

Working out which of those situations applies requires listing every income source and noting which increase and which do not, which is a short exercise rarely done.