Unitary models, assuming a single objective function and unified budget constraint, are traditionally used to model household behavior. Most empirical tests of unitary models rely on endogenous regressors. This paper uses an exogenous change in the intrahousehold distribution of income, provided by a change in U.K. Family Allowance policy. Expenditure shares are estimated for a wide range of goods. Shifts in expenditure shares for assignable goods, such as men?s clothing, children?s clothing, and men?s tobacco, suggest that children benefited at the expense of men when this policy change shifted income within households from men to women.