to the baseline, because they were listed in the baseline either under a di¤erent name or under a di¤erent family. This implies that matching was imperfect and that the total enrollment rates for preschools from this study are biased downward for baseline children. However, there is no reason to think that name changes a¤ected schools disproportionately depending on their treatment status, so this problem is unlikely to a¤ect the ITT estimator.

In 2000, 3176 out of 4243 (74.9 percent) school participants were matched to a child in the baseline. An additional 337 pupils (7.9 percent) were living in a baseline household but could not be found in the baseline. These children were either forgotten during the baseline enumeration, or they joined the household of the baseline parent after the start of the program. The children who were found in school but were matched neither to a baseline child nor to a baseline household (17.2 percent of those found in school) can be children from families that were “forgotten” during the baseline enumeration or children whose household did not belong to the school’s catchment area but transferred to the school. In 2001, the overlap between the baseline and the set of pupils found in school is smaller than in 2000. Just 2988 pupils out of 6333 (47 percent) school participants were matched to a child in the baseline, while an additional 974 (15.4 percent) were matched to a baseline household but not to a baseline child. The decrease in overlap is not especially worrying, since the unmatched children will include a new cohort of children who are the eldest in their families, as well as the 2000 cohort of eldest children, and the siblings of the 2000 cohort of oldest siblings.<sup>30</sup>

# 4.3 Transfers of baseline children

In Busia and Teso districts, the potential for transfers between schools is high because of the high density of schools. A primary school has on average 7.9 other schools within 4 km, while the number for preschools is slightly higher. This makes it quite easy for children to switch between schools, even though most children go to school on foot. Other projects in the same region<sup>31</sup> ...nd a rate of transfers of 6 percent per year for with primary schools. In this section, we investigate the magnitude and implications of transfers of baseline children. Section 6 elaborates on the implications of transfers of children who do not belong to any baseline.

There are three classes of transfers of baseline children that might bias the results in this

> get dropped as children grow up. Children also change names for religious reasons, if they or their parents become saved Christians. It is also quite common for children to transfer between households. Due to cultural practice and to the very high incidence of deaths due to HIV/AIDS among young adults in Western Kenya, a high proportion of children live with a guardian who is not their biological parent. The 1998 DHS survey found that approximately 10 percent of Kenyan children did not live with either of their biological parents.

> 30 We will investigate the e¤ect of new cohorts moving into the schools when the Kenya census data are available.

> 31 See for example Miguel and Kremer (2001) or Glewwe, Kremer, Moulin and Zitzewitz (2000)

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