How does Chiappori's collective model of household labor supply differ from the traditional unitary household model, and why does the distinction matter?
Think about your answer, then reveal below.
Model answer: The unitary model treats the household as a single decision-maker with a single utility function, as if household members pool all income and maximize joint utility. Chiappori's collective model recognizes that households contain multiple members with potentially different preferences, and models household decisions as the outcome of a bargaining process. Each member has their own utility function, and the household allocation is Pareto efficient — no member can be made better off without making another worse off. The sharing rule determines how household resources are divided, and it depends on each member's bargaining power (influenced by outside options such as divorce value, own earnings, welfare benefits, and marriage market conditions). This matters because it predicts that changes in women's outside options (e.g., divorce law reform, female wage growth) shift the sharing rule and affect labor supply even if total household income is unchanged — a prediction the unitary model cannot make.
The collective model explains empirical findings that the unitary model cannot: income in the wife's name affects spending differently from income in the husband's name (violating income pooling), changes in divorce laws affect married women's labor supply (through bargaining power, not direct applicability), and conditional cash transfers targeted to women change household behavior differently from transfers to men. The model also provides a framework for understanding the relationship between female labor force participation and women's economic empowerment — when women's labor market opportunities improve, their bargaining position within the household strengthens, which further encourages participation.