Program Evaluation with Unobserved Heterogeneity and Selective Implementation : The Mexican Progresa Impact on Child Nutrition

The assessment of the impact of social programs is the subject of lively, sometimes heated debate over whether program evaluation is best conducted either by comparing mean outcomes from a randomized intervention or by using econometric techniques with nonrandom samples. This paper contributes to this debate through an examination of PROGRESA, a Mexican anti-poverty and human resource program, on child nutritional status. PROGRESA was randomly assigned at the locality level. However, a shortage in the availability of one component; a nutritional supplement provided to preschool children; led local administrators to exercise discretion in its delivery, systematically favoring those children with poorer nutritional status. While comparisons of mean outcomes suggest that PROGRESA had no or a negative effect on nutritional status, estimates that control for this heterogeneity using child specific fixed effects find that PROGRESA had significant and substantial positive impacts in increasing stature. The long-term consequences of these improvements are non-trivial; its impact working through adult height alone may result in a 2.9% increase in lifetime earnings