We develop the concept of relative resource shares, defined as the fraction of total adult expenditure that women command within a household, to demonstrate the identification of individual-level consumption inequality from repeated cross-sectional data. To recover relative resource shares from expenditure data, we introduce a new assumption of weak similarity of preferences across people that requires individuals’ preferences to be similar whether they are in a couple or not. This assumption is shown to be weaker than those used in the existing literature, yet sufficient to recover the relative contributions of changes in characteristics, and changes in the resource share function, to the evolution of relative resource shares over time. We apply this new methodology to estimate within-household gender inequality in Great Britain from 1978 to 2019. Women’s relative resource shares are estimated to have increased by 12–13 percentage points over this period, rising from disparity to roughly parity with men. As a consequence, individual-level inequality rose by less than household-level inequality. We find that changes in characteristics related to women’s bargaining power play a key role in explaining these changes. We document strong differences between childless women and mothers.