Standard price indices (CPI/HICP) measure changes in the price of a fixed basket of goods but implicitly assume constant product lifetimes. If goods become less durable, the real cost of maintaining a constant standard of living increases even when unit prices remain stable. We introduce the Household Durability Index (HDI) and the Unit of Constant Effort (UEC) — hours of work at median wage required to maintain a constant domestic stock. Using aggregate data from the Spanish Household Budget Survey (INE, 2006–2023), we find that the counterfactual cost of maintaining the 2006 stock at 2023 prices and current product lifetimes is 51% higher than it would be at 2006 lifetimes, equivalent to 9 additional working days per year. Quintile analysis confirms a regressive mechanism: the poorest quintile is the only income group where replacement effort has increased (+30.3%), while the richest quintile has reduced it by 21.9%. We interpret durability inflation as a form of invisible, regressive cost-of-living increase with implications for poverty measurement, consumer protection policy, and the right-to-repair agenda.
THOMAS BLACKWOOD (Wed,) studied this question.