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Chapter 6 - Currie/Thomas Econometric Studies
Introduction to the Original Evaluation (Excerpt)
The federal Head Start program, started in 1965, seeks to enhance "the social and cognitive development of children through the provision of educational, health, nutritional, social and other services to enrolled children and families." In a series of studies, University of California, Los Angeles economists Janet Currie, Duncan Thomas, and Elana Garces (the "UCLA team") used econometric statistical models to analyze data from three large, nationally representative surveys to estimate the impact of Head Start. The surveys were the National Longitudinal Survey of Youth (NLSY), the Supplemental National Longitudinal Survey's Child-Mother file (NLSCM), and the Panel Study of Income Dynamics (PSID). The UCLA team estimated the impact of Head Start on children who participated in the program by examining a range of short-term and long-term outcomes. The first study used data from 1986 and 1990, the second used data from 1979-1990, and the third used data from 1968forum moderator and our discussion guidelines1977. The authors compared children who participated in Head Start to those who did not, statistically controlling for socioeconomic differences and other factors. They conclude that Head Start participation was associated with a number of positive cognitive effects for both white and black children, but that these gains diminished over time for black children. Long-term findings include improved school performance for white children and a reduction in criminal activity for black children. The studies used large, nationally representative data sets; however, the methodology used (sibling comparison) resulted in a sample that was not nationally representative. In addition, there are a number of methodological problems, including (1) possible selection bias if the parents enrolled either the less able or the more able sibling in Head Start, (2) the possibility of parents making "compensating investments in the non-Head Start child;" (3) spillover effects from the siblings in Head Start sharing what they learn with the sibling not in Head Start; (4) data quality questions in the NLCSM because, in different waves of the study, mothers gave different responses to the same question concerning their child's Head Start participation; and (5) serious non-random attrition in both the PSID and NLSY. Thus, these findings are subject to considerable uncertainty, especially because they find long-term impacts for white children and not for black children, even though most experimental studies find positive impacts for black children. Hence, these studies should be viewed as suggestive only.
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