A one-off bonus barely changes your spending — Milton Friedman explained why

Friedman argued people don't set spending by this month's paycheck, but by their estimate of long-run, 'permanent' income averaged over a lifetime. A temporary windfall like a tax rebate mostly gets saved rather than spent, because it doesn't shift that long-run estimate. The theory reshaped how economists — and governments planning stimulus payments — think about consumer behaviour.

— Milton Friedman, A Theory of the Consumption Function — Princeton University Press, 1957
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