age at entry or exit). Empirical evidence has mainly focused on US data, since the United States census is very detailed and has been available for several decades. Leon (2004) accounts for the endogeneity of schooling by instrumenting it with the changes in state compulsory laws as a source of exogenous variation. He concludes that 3 years of additional schooling result in one less child per woman. McCrary and Royer (2006) show that female education entails small and possibly heterogeneous improvements of women’s fertility and infant health, using school entry policies as an instrument for education. They exploit the fact that in Texas and California, the year at which a child starts school is dependent on his exact day of birth: children aged five on December 1<sup>st</sup> (California) or September 1<sup>st</sup> (Texas) can start their first year of kindergarten while the others will have to delay their entrance by one more year. This sharp discontinuity allows the authors to compare the outcomes of children born just before the cutoff date and just after, children who will have different level of education throughout school enrollment. Over the sample of teenagers affected by the change in rule, education does not seem to have a significant impact on fertility. Moreover, age at first birth seems to be the same before and after in the Californian sample, a little higher for women born after September 1<sup>st</sup> in Texas (22.5 versus 22.6).

# 2.3.2 Unobservable common factors

**_The socioeconomic and cultural environment of a woman’s childhood place of residence is expected to influence her general health and well-being, and contributes to the formation of beliefs, aspiration and practices that will be important during teenage and adult years_** (Caldwell and Caldwell (1987)). Mahy and Gupta (2002) investigate the trends and differentials in reproductive behavior among adolescents in Sub-Saharan Africa, drawing on data from successive DHS. The authors conclude that there was a slight decline in the probability of teenage childbearing, the age at first union and first child. The findings suggest that (female) adolescent sociodemographic characteristics, such as education, place of residence, exposure to mass media, had greater influence on early reproductive outcomes while the contextual variables had weaker influence. Secondary schooling had among the strongest and most consistent negative effect.

In the case of Kenya, cultural norms are strongly linked to one’s belonging to an ethnic group, of which Kenya counts 7 major (covering 85% of the population): Embu, Kalenjin, Kamba, Kisii, Kiyuku, Luo and Luhya. Previous studies on fertility have revealed that desired family size is smaller among the Kamba, Kikuyu, Luhya compared to Luo, who use contraception to a lesser extent than other groups (Fapohunda and Poukouta (1997)). In terms of educational achievement, the Kikuyu are the best educated, followed by Kamba, both of which had early access to colonial education (Fapohunda and Poukouta (1997)). The smaller ethnic groups<sup>5</sup> but Taita/Tavate show much lower levels of education (see Table 1).

# 2.3.3 Through which channel does education affect early fertility?

W **_hile it is clear that schools play an active role in the education and socialization, little progress has been made to date in identifying what aspects of education are transforming in ways that ultimately matter for the timing of marriage and childbearing_** . One exception is the paper from Black et al. (2004). The paper looks at the consequences on fertility reduction of policies that increase educational attainment. From 1924 to 1974, compulsory schooling requirements in the United States varied by state: 20 of them changed at different times the minimum dropout age which varied from 14 to 18. In Norway, an educational reform was passed in 1959 to raise the minimum dropout age from 14 to 16 years. Municipalities were free to choose when they wanted to implement the new system but had to complete it by 1973. Using the

> 5 “others”, i.e. Masai, Meru, Mijikenda/Swahili, Somali, Turkana, Kuria.

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