My initial response to the idea that women should pay lower tax rates than men was skeptical. But Sara liked it, so I read more. It's certainly intriguing. Some responses to critics are available here. Download the paper (PDF) by Alberto Alesio et. al. to learn more. The abstract:
Gender Based Taxation (GBT) satisﬁes Ramsey’s optimal criterion by taxing less the more elastic labor supply of (married) women. This holds when diﬀerent elasticities between men and women are taken as exogenous and primitive. But in this paper we also explore diﬀerences in gender elasticities which emerge endogenously in a model in which spouses bargain over the allocation of home duties. GBT changes spouses’ implicit bargaining power and induces a more balanced allocation of house work and working opportunities between males and females. Because of decreasing returns to specialization in home and market work, social welfare improves by taxing conditional on gender. When income sharing within the family is substantial, both spouses may gain from GBT.
Probably not a realistic option.