Wednesday, June 8, 2011

Children's stories

Via those emails that I continue to receive comes Marian Wright Edelman, boss of the Children's Defense Fund, defending Head Start.

My primary concern today is not whether or not Head Start should be cut, it is with how Edelman makes her argument. In particular, Edelman offers two sorts of evidence. The first consists of a moving anecdote about someone called Angelica Salazar:
The colors were brighter than any she had seen before. Shapes, letters, and lots and lots of colors adorned the walls. Around the room, children worked together building high rises with colored blocks and "reading" colorful picture books.

"I had never seen so much color," Angelica Salazar recalls of her first days as a Head Start preschooler in Duarte, California. She remembers her discovery of library books and spending hours curled up on the reading rug. Head Start provided her first formal English instruction. Her parents, who spoke mostly Spanish, enrolled her in the program knowing that their little girl would need to master English to succeed in school.
Anecdotes play a surprisingly large role in policymaking but they are, of course, entirely irrelevant. Anecdotes typically confuse outcomes (Y1 in the usual notation) with impacts (Y1-Y0, or the difference between the outcome with the program and the outcome without it). Put differently, anecdotes ignore the counterfactual of what would have happened in the world without the program. In the case of Angelica, her parents might have found another program, or maybe she would have done just as well with just K-12 education. The difference between outcomes and impacts is remarkably hard for people to grasp. Even in the face of experimental evidence of ineffectiveness, program operators will often insist that they know a program works because of the outcomes they have observed among participants.

The second sort of evidence offered up by Edelman consists of a brief reference to a completely different program:
Early childhood programs significantly increase a child's chances of avoiding the prison pipeline that Angie now studies as a policy expert, and investments in quality early education can produce a rate of return to society significantly higher than returns on most stock market investments or traditional economic development projects.
Edelman does not say what this program might be, but it is presumably Perry Preschool. Jim Heckman and some of his recent students have thoroughly reanalyzed the Perry data, bringing to the discussion a level of rigor and seriousness unfortunately often missing from the advocacy research of the program's developers. When they are done, Perry does indeed pass cost-benefit tests and have a positive rate of return. But Perry is not Head Start. Perry was much more expensive than Head Start, featured different sorts of instructors, served a different and more disadvantaged (particularly cognitively) population and included interventions with parents. There are also important unanswered questions about the extent to which it could be effectively scaled up. Perry is not irrelevant to Head Start, but Edelman is being dishonest by writing as though they are the same thing while ignoring the evaluation record on Head Start itself. On their own, the Perry findings certainly support expenditures on research; any relevance to Head Start funding is speculative.

On the substantive question, the literature on Head Start is mixed at best. Michael Baker of Toronto gave a very nice talk at the Canadian Economic Association meetings last weekend that reviewed the serious literature on early childhood interventions. If you are willing to wait awhile, the talk will be published in article form in the Canadian Journal of Economics. In the meantime, the experimental evaluation of "early Head Start", helpfully summarized at the Institute of Education Sciences' What Works Clearinghouse is a good place to start.

In sum, Edelman's piece has value mainly as an example of an attempt to distort evidence and mislead readers. Her closing appeal to "values", like appeals to "fairness" in similar contexts, is the last refuge of an evidence-avoiding scoundrel. And what of Evidently scientific socialism, as they used to call it, has been tossed overboard for the simpler pleasures of sentimental socialism, in which reason and evidence are replaced by heartwarming bedtime stories. Sigh.

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