Among policy analysts, the Perry Preschool Project is one of the most famous randomized control trials ever undertaken. In the 1960s, over 100 disadvantaged black children in Michigan were randomly selected to receive additional education and support starting at age three.
What makes this study unique is that researchers have been able to follow up with the participants in both the treatment and control groups for decades after the formal program ran its course. This means that we can directly see how this program influenced outcomes like adult wages directly, instead of relying on intermediary effects like school test scores.
What’s even better is that there is robust data not only on the control and treatment groups, but on those peoples’ siblings and children. This makes the Perry Preschool Project not only one of the best studies ever conducted for understanding the effects of early childhood education, but it also makes it one of the best examples of how programs focused on benefiting disadvantaged children can have effects that spillover to nearby children and even the next generation.
Results from the most recent follow-up survey have been analyzed and published in a new working paper. Today, I want to explain what these effects are, and what the implications might be for related policies.
Intergenerational Effects
The larger of the two spillover effects was how the Perry Preschool Program influenced outcomes for the children of the participants. The way this was measured was by comparing adult outcomes such as employment for the children of participants in the control and treatment groups.
The researchers found that children of people in the treatment group were more likely to be employed as adults, were more likely to be in good health, they were less likely to be divorced, and perhaps most importantly they were less likely to be arrested.
Additionally, male children of people in the treatment group were more likely to have a college degree, while female children were more likely to have a highschool degree.
What's so exciting about these intergenerational effects is that despite not taking place until over 50 years after the intervention, and therefore being subjected to over 50 years of discounting, they still have massive and positive net present benefits.
Sibling Effects
When exploring the effect that the Perry Preschool Project had on participants' siblings, the researchers chose to limit themselves to a subset of all siblings. Specifically, they only considered siblings that were older than the participants, but not more than 5 years older.
The justification for this small range is that (1) Younger siblings might experience different outcomes because their parents might act differently after participation in this program (a worthwhile effect to understand but not the effect they were interested in) and (2) Children more than five years older might already be experiencing some of these outcomes.
The most notable sibling effects are that female siblings of participants were more likely to finish high school and male siblings were less likely to have been arrested. The effect sizes for siblings are smaller than those for children of program participants, but they still make a big difference.
From a policy perspective, there are a few key takeaways from this research. First, we may be underestimating the value of anti-poverty programs. The intergenerational effects of these projects is enormous, and unless we account for that we are likely not accurately portraying the benefits of many projects.
Second, we should be aware of who we are enrolling in pilot programs. The total benefits of programs will often spillover into nearby people and communities. On one hand, targeting communities to maximize these spillover effects will likely increase the value of a project, but we must also be careful and understand that if these effects exist, then people or communities with less opportunity for spillover might have smaller effects.