When a girl can go to school, she improves not only her own live, but also the live of her children, her relatives, her society. This is what we call ‘the girl effect': the powerful social and economic change broad about when girls have the opportunity to participate. Research in developing countries has shown a consistent relationship between better infant and child health and higher levels of schooling among mothers. When a girl in the developing world receives seven or more years of education, she marries four years later and has 2.2 fewer children. An extra year of primary school boosts girls' eventual wages by 10 to 20 percent. An extra year of secondary school: 15 to 25 percent. When women and girls earn income, they reinvest 90 percent of it into their families, as compared to only 30 to 40 percent for a man.