A recent Vox article by Libby Nelson made some useful points about pre-K, but also encouraged some misconceptions.

The article pointed out that in many benefit-cost studies of pre-K, for example of the Perry program and the Chicago CPC program, a major share of the estimated benefits is anti-crime benefits. The article pointed out that these anti-crime benefits did not occur for the Abecedarian program. Finally, the article argued that Perry is a small-scale expensive program, and argued that Chicago CPC was an ages 3-9 program, implying that therefore it would be hard to expect high benefits from less intense large-scale pre-K programs.

It is certainly true that a major benefit of some pre-K programs is reduced crime, and this did not occur for the Abecedarian program. It is also hard to argue with the article’s contention that “providing quality pre-K is more difficult than enrolling children in any kind of early childhood education”.

However, many readers may mistakenly think this means that high benefit-cost ratios for pre-K depend upon these anti-crime benefits. As I have argued in my 2011 book, Investing in Kids, my forthcoming 2014 book From Preschool to Prosperity, and in this blog, there are numerous pre-K programs that have benefits much greater than costs based solely on their benefits for adult earnings.

Adult earnings benefits greater than costs are found for the Perry program, the Chicago CPC program, Deming’s study of Head Start, and the Abecedarian program. Based on test score effects, which are a conservative estimator of adult earnings, adult earnings benefits greater than costs are estimated for state and local pre-K programs in Boston, Tulsa, North Carolina, and many other states.

Adult earnings benefits are even greater if we account for spillover effects of some workers’ skills on boosting overall productivity and wages in the economy.

These high adult earnings benefits greater than costs are for state pre-K programs that are large-scale, and that are not as intense as the Perry program. In addition, the Chicago CPC program shows large adult earnings benefits, as well as anti-crime benefits, for the part of the program that was only pre-K at ages 3-4, disregarding the ages 5-9 component of the program.

The article mentioned that the control group in the Abecedarian study had a low crime rate. The article did not mention that this might imply that Abecedarian’s small anti-crime effects might not be typical of pre-K programs targeted at high-poverty neighborhoods. We would expect the control group in such neighborhoods to have higher baseline crime rates, without the pre-K program. Pre-K programs have more potential in such cases for reducing crime.

My economic argument for pre-K in my various writings has not relied on anti-crime effects of pre-K at all, not because I don’t think they exist, but because I’m trying to focus on what pre-K does for earnings. Pre-K has a very high benefit-cost ratio disregarding any anti-crime benefits, and these high benefits can be achieved with large-scale and less intense programs.