Short answer: sexism. Human rights campaigners and researchers complain that traditional data collection is leaving a patchy picture of women’s lives. Employment surveys, for example, often ignore housewives who also have part-time jobs, and many official stats fail to break down results by gender. It’s difficult to tackle problems like domestic violence and maternal mortality without proper measurements. So the U.N. is enlisting 10 countries to test a new framework for enumerating unpaid work, like cooking and cleaning, to begin filling the female data gap.