Optimal income taxation when couples have endogenous bargaining power

This study examines the optimal income taxation for a two-earner household, where the couple bargains over their private goods consumption and time allocation between work and leisure. In the model, bargaining power is determined endogenously by the income gap between the two earners. Conventional studies have shown that the higher income tax rate should be imposed on the individual with the smaller wage elasticity, typically the individual with the higher productivity. In contrast to conventional argument, this study shows that the optimal tax rate on the household member with the higher productivity is lower than that of the individual with the lower productivity if the required tax revenue is relatively small and the influence of the gender income gap on the power balance of the couple is moderate. This is because such a tax structure encourages the labor supply of the individual with the higher productivity to mitigate the decrease in the household's consumption induced by income taxation.