The direct benefits that come from investing in girls' education are vast but there are also indirect benefits to the investment including, reproductive health for women, decreasing infant mortality, and decreasing family size. The longer a girl stays in school the better able she is to delay early marriage and pregnancy. "Secondary school has a more consistent and stronger effect on delaying childbearing, increased use of contraception, desire for fewer children, and actual reduced fertility." (Wagner 2008: 8) Pregnancy in young females is a life altering experience and costs the economy exorbitant amounts; it limits her lifetime earning potential and her engagement as an economic actor. Therefore, the delay in childbearing can dramatically decrease cost and expenses and in turn eliminate poverty. A recent study done by the Nike Foundation and the World Bank shows that, "pregnancy among girls and young women costs Kenya about $500 million annually, while investing in girls could add $3.2 billion to its economy." Education can provide girls with the opportunity to think, be engaged with knowledge and learn about family planning and safe contraceptives. An article written by Ruth Levine, Educating Girls, Unlocking Development, speaks further about the "inverse relationship" between women's education and fertility and how the "completion of primary school is strongly associated with later age at marriage, later age at first birth and lower lifetime fertility." When girls' are able to complete primary education they gain the knowledge needed to better their lives and take care of themselves and their families. In turn, lower fertility and later age of first birth is extremely beneficial to the country as economic costs are decreased, money is saved, and poverty is reduced.