Retirement planning often assumes spending equal to a fixed proportion of final salary, held constant thereafter. Observed spending patterns rarely behave that way.
The composition changes at the transition
Work-related costs such as commuting, professional clothing and workplace meals fall away. Contributions to retirement saving also stop, which was a substantial share of gross income.
Against that, time available for discretionary activity increases sharply, and so does spending associated with it. Housing and utility costs can rise with more hours spent at home.
The total may land near a familiar proportion, but the underlying mix is different enough that assuming continuity misstates individual categories.
Discretionary spending tends to front-load
The early years of retirement typically carry the highest discretionary spending, with travel and activity concentrated while health and energy permit.
This tapers over time in a way that is fairly consistent across households, though the pace varies. Spending drifts downward in real terms through the middle period.
A plan assuming flat real spending therefore overstates the middle years and can understate the early ones.
Care costs can reverse the trend late
Later retirement can bring costs that rise sharply, particularly where support with daily living or residential care becomes necessary. These are concentrated and can be large.
The probability and scale vary enormously between individuals, which makes averages unhelpful for planning any specific case.
The combination of falling discretionary spending and potentially rising care costs is why the spending path is often described as curved rather than flat.
Inflation applies unevenly
A general inflation measure reflects a broad basket that may not resemble a retired household's actual purchases. Weighting differs, particularly for utilities, healthcare and services.
Where the categories a household relies on rise faster than the general measure, purchasing power falls even when income is uprated in line with the headline figure.
This effect compounds over a long retirement, which is why the assumed inflation rate is one of the most consequential inputs in any projection.
Why the assumption deserves testing
A single fixed proportion is convenient for calculation and easy to communicate, which is why it persists. It is a starting point rather than a finding.
Building a plan from actual current spending, adjusted for the categories that will genuinely change, produces a more defensible figure than applying a general ratio.
Because tax treatment, state provision and care funding differ by jurisdiction and change over time, individual planning warrants professional input.