Weighing the preschool research evidence

Professor Bruce Fuller had an op-ed on preschool in the Washington Post on February 9. Professor Fuller’s interpretations of preschool research omit some important research.

Specifically, Professor Fuller argues that “youngsters from middle-class and well-off homes benefit little from preschool”.  He goes on to say that “young children attending quality half-day programs display the same learning gains as those attending full-day programs”.  Therefore, “we must avoid squandering scarce dollars on full-day programs for children who gain little from preschool”.

Professor Fuller cites some studies that support his arguments. But he fails to mention other studies that go against his arguments.

For example, Professor Fuller does not mention the research studies in Tulsa and Boston that find that universal preschool produces benefits for middle-class children that are only slightly less than the benefits for low-income children. Professor Fuller also does not mention a research study from New Jersey that finds significantly greater benefits from full-day preschool compared to half-day preschool.

An obvious and important question is: which studies should you believe? Should we believe the studies that Professor Fuller cites, or the studies that I cite? Or should we just say that the evidence is mixed and uncertain, which can be interpreted as an argument for inaction until more research is done?

The key problem in any preschool research is what social scientists call “selection bias”. The families that choose preschool differ from those who do not choose preschool, due to both family characteristics that we can observe, and family characteristics that we can’t observe. In addition, programs may choose to select preschool participants due to both observed and unobserved family characteristics.

For example, perhaps families that are more ambitious choose preschool. Or perhaps some preschool programs try to choose children who are easier to manage. Either source of selection would tend to mean that preschool participants will tend to do better than non-participants because of pre-existing family and child characteristics, above and beyond the true effect of the preschool program. Selection bias in estimating program effects would be positive.

Alternatively, perhaps families that are having more trouble with their children tend to try to put their children in preschool. Or perhaps preschool programs with a social mission try to choose needier children. These sources of selection will tend to produce a negative selection bias in estimating the true effects of preschool.

How can this selection bias be dealt with? If there are infinite resources and time, the ideal method is a large and perfectly-run randomized control trial. Preschool applicants would be randomly divided into a treatment and control group. As a result, we would expect average observed and unobserved characteristics in both the treatment and control group to be similar, and as the sample size gets larger, that expectation is increasingly likely to be realized.

But randomized trials are expensive and difficult to run, particularly on a large scale. Therefore, an alternative is to rely on natural experiments, in which some aspect of the world has resulted in different children having differing access to preschool, for reasons that have nothing to do with unobserved characteristics of the child and his or her family.  The treatment and comparison groups, with different access to preschool, will differ in preschool participation, but not observed and unobserved characteristics, and therefore we can interpret the outcome differences as being due to preschool, not pre-existing differences between the two groups.

A third method of trying to control for selection bias is to control for observed characteristics of the child and family.  Such controls help, but by their very nature cannot control for unobserved pre-existing differences between the treatment and comparison groups. Hence, such estimates may be subject to selection biases of unknown size and sign.

The Tulsa and Boston evidence that I am citing on middle-class benefits is based on natural experiments. Access to preschool and to kindergarten is based on an age cutoff.  The essence of the methodology used in these two studies is to compare the test scores of children who just missed the kindergarten age cut-off and are therefore just entering preschool, with test scores of similar children who just made the kindergarten age cut-off, who are just entering kindergarten, and who participated in preschool the preceding year.  These two groups are arguably similar in unobserved as well as observed characteristics because they were similarly selected into the same preschool program. The timing of their preschool access was based on age, and a few days of age in either direction should not make a big direct difference in test scores. The “jump” in test scores that is observed for the slightly older group in such studies is therefore reasonably attributable to the preschool participation the preceding year.

The New Jersey evidence I am citing on full-day versus half-day preschool is based on a randomized control trial. Excess applicants for a full-day preschool opportunity were randomly assigned to either receive full-day preschool, or only receive half-day preschool. The results showed significantly greater test score effects of full-day preschool. In Bartik (2011), I used these estimates to predict that full-day preschool produces 56% greater earnings benefits than half-day preschool.  Therefore, there are some diminishing returns to preschool time (benefits are not doubled), but there are benefits to full-day preschool over half-day preschool.

Most of the evidence that Professor Fuller cites is from the third category of studies, which only can control for observable child and family characteristics. These studies may be biased upwards or downwards by selection bias. Therefore, I would not weigh these studies as heavily.

In my view, the research studies that should receive the greatest weight use randomized or natural experiments to examine the causal effects of preschool, which avoids problems due to selection bias. The research studies that use such evidence support middle-class benefits of preschool, and support greater benefits for full-day programs.

Posted in Distribution of benefits, Early childhood program design issues, Early childhood programs | 4 Comments

What the available evidence shows about middle-class benefits of early childhood education

At the recent Education Writers Association conference on early childhood education, Russ Whitehurst of the Brookings Institution cited Tulsa and Boston studies as evidence that the benefits of early childhood education are much greater for low-income children than for middle-class children.

This is incorrect. The Tulsa and Boston studies actually provide evidence that the benefits of early childhood education are only modestly less for middle-class children than for lower-income children. In Tulsa, the research, in a paper on which I was a co-author, suggests that the test score boost from full-day pre-K for middle class children is about 88% of the boost for lower income children. In Boston, Weiland and Yoshikawa’s research suggests test score benefits of Boston’s full-day pre-K program for middle-class children are 71% of the benefits for lower-income children.

These test score benefits for middle-class children are sufficient to predict adult earnings gains that will be many multiples of costs. The Tulsa study calculates that the ratio of the present value of future adult earnings benefits to program costs for full-day pre-K is 2.82 for middle-class children, which is only modestly less than the 3.09 ratio for children eligible for a free lunch.  For Boston, my analysis of Weiland and Yoshikawa’s findings suggest that the ratio of the present value of future adult earnings benefits to costs for Boston’s full-day pre-K program is 2.30 for middle class children, versus 3.22 for children eligible for a subsidized lunch.

A key point in both findings is that the ratio of predicted future adult earnings benefits for middle class children to program costs is much greater than one. Providing free, high-quality pre-K to middle class children can be rationalized because economic benefits exceed costs. Universal pre-K may also win middle-class votes and support, but universal pre-K can be rationalized on its economic merits rather than just on political expediency.

I know of no other evidence that allows a direct comparison of the relative benefits of pre-K for middle-class and lower-income children. There is one study of pre-K for middle-class children in Utah that shows some benefits.

There might be various reasons why the social benefits of pre-K for lower-income children are much greater than for middle class children, even if the dollar earnings benefits are similar. Lower-income children would be predicted to have baseline adult earnings that are lower, so a similar dollar benefit will be a larger percentage boost to adult earnings.  In Tulsa, our study predicts that the percentage boost to adult earnings for children eligible for a free lunch is over 10%, whereas the percentage boost for middle-class children is between 5 and 6%. We might judge that providing extra dollars to lower income children is more valuable because it has a more dramatic impact on their future well-being.  In addition, it is a plausible hypothesis that pre-K may have greater benefits in reducing crime and welfare usage for children from lower-income families than for middle-class children, although I know of no empirical evidence for or against such greater relative benefits.

For child care programs, Duncan and Sojourner’s study of the Infant Health and Development program suggests that this program only boosts test scores for lower-income children. For parenting programs, studies of the Nurse Family Partnership suggest that NFP only works for lower-income families, not middle-class families.  Pre-K may be different from child care and parenting programs because pre-K may provide social and cognitive learning in a group setting that is hard for many middle class families to duplicate on their own.

The evidence is sparse on the absolute and relative benefits of early childhood education for middle-class children. This evidence is always likely to be sparse because there is not great interest from government or the philanthropic community in sponsoring extensive research on how early childhood education affects the middle class.  But the available evidence provides some economic support for universality in pre-K programs, while the pattern of benefits for children would argue for targeting child care and parenting programs on lower-income families.  Considering how programs benefit parents might alter these calculations for relative benefits and costs for different income groups, and is an important topic for future research.

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The research consensus on early childhood education

On February 3, 2014, I spoke at a conference on early childhood education sponsored by the Education Writers Association. Later, the conference heard from many other speakers, including Russ Whitehurst of the Brookings Institution.

Whitehurst expressed uncertainty about whether early childhood education has lasting impacts. Journalists listening to Whitehurst might conclude that there is no research consensus on the impacts of early childhood education.

In my opinion, there is a research consensus that high-quality early childhood education can have lasting impacts. Whitehurst’s perspective represents a minority of researchers who dissent from what the bulk of the research shows.

Whitehurst’s position is based on emphasizing two studies, while downplaying all other research studies. He emphasized the Head Start randomized control trial and the Tennessee pre-K randomized control trial. These studies found immediate impacts of pre-K, which faded over time.

However, most good studies do find lasting impacts of early childhood education. These studies include the two best-publicized randomized control trials of early childhood education, the Perry Preschool study and the Abecedarian study.

Whitehurst’s presentation implied that Perry and Abecedarian are less relevant because they were done a long time ago. But early childhood studies that look at adult impacts up to 36 years later necessarily must have been started a long-time ago.

Whitehurst also implied that the two studies are less relevant because they provided services that differ greatly from what early childhood education programs are today. But the Abecedarian program is quite similar in services offered to the present-day Educare program.

And Perry Preschool does not differ in kind from many pre-K programs today. It had lower class sizes than most of today’s programs, and provided services for ages 3 and 4 rather than just age 4.  But it is similar to many of today’s programs, for example programs in Tulsa, Boston, and the Chicago Child-Parent Center in using certified teachers paid public school wages. And Perry was only a half-day program whereas Boston’s program is full-day and Tulsa’s program includes many full-day centers.

Perry’s program had an estimated 19% effect in increasing adult earnings.  The larger class size and one-year nature of many of today’s pre-K programs might somewhat decrease adult earnings impacts, while a full-day program might increase adult earnings impacts. Based on what we know about how class size, full-day vs. half-day, and two years versus one year affects impacts, we might think that many of today’s pre-K programs might have somewhat lower adult earnings impacts than 19%.  But even an impact of 6% or more (which is what we tend to find in the studies of pre-K reviewed below) would have a very high ratio of benefits to costs.

More importantly, there are many other studies than Perry and Abecedarian that show that early childhood education can have lasting impacts.  These include the Infant Health and Development Program, also a randomized control trial, as shown in a recently published study by Duncan and Sojourner.

These other studies also include many other studies which are not randomized control trials, but which do have very good comparison groups.  These studies are “natural experiments”, in which whether or not a child participates in early childhood education is determined by the accidents of geography or age or other circumstances that are likely unrelated to unobserved characteristics of the child or family. These natural experiments provide good evidence because the lasting differences between the treatment group and the comparison group are most plausibly attributed to the program’s true causal effects, as there is no good reason to think that there are significant unobserved pre-existing differences between the treatment group and the comparison group. Natural experiments that show lasting impacts of early childhood education  include the many Chicago Child-Parent Center studies, studies of Head Start by Deming , Currie et al. and Ludwig et al. , and a study of North Carolina’s early childhood programs by Ladd et al.

Many of the research studies that find lasting impacts of early childhood education also find that cognitive test score impacts fade over time.  Test score fading is found in Perry Preschool, the Abecedarian program, the Chicago Child-Parent Center program, and in Deming’s study of Head Start. Despite test score impacts that fade during the K-12 years, all these studies find large impacts of early childhood education on adult outcomes, with these impacts being “large” in the sense that they either directly show large percentage adult earnings impacts, or have educational attainment impacts that would predict large percentage adult earnings impacts.

Therefore, contrary to the impression left by Whitehurst’s presentation, there is a significant research basis for believing that even if there is fading in the Head Start randomized control trial and the Tennessee pre-K randomized control trial, there may well be later large effects on adult outcomes.  The most plausible theory for test score fading but long-term adult benefits is that early childhood education leads to lasting impacts on “soft skills” (social skills, character skills). These lasting soft-skill effects are extremely important in determining adult outcomes in higher educational attainment and higher employment rates and wage rates.

In the case of Head Start, the 3rd grade cognitive test score impacts, while mostly statistically insignificantly different from zero, are large enough that they would predict over a 1% impact on adult earnings, which would be a lot of money over a person’s entire working career. If these are faded impacts that significantly underpredict adult earnings impacts, the true adult earnings impact could be much greater. In addition, the confidence interval on these 3rd grade test score impacts is large enough that while it cannot rule out zero impacts, it also cannot rule out test score impacts that would predict a 2 to 3% increase in adult earnings. Therefore, the Head Start impacts are consistent with both zero test score impacts at third grade, and with test score impacts that would be large enough to be relevant for policy purposes.

The research literature also suggests that the early post-program impacts of early childhood education on test scores are better predictors of long-term impacts on adult earnings than are later, faded test score impacts. This finding occurs in the Chicago CPC study, the Abecedarian study, the Perry study, and Deming’s Head Start study. This finding also occurs in Chetty et al.’s study of the adult earnings impacts of higher kindergarten quality.

Therefore, the many recent “regression discontinuity” studies of state and local pre-K that show large effects on kindergarten entrance test scores adds some additional support to the notion that pre-K has large impacts. (These studies include studies by the National Institute for Early Education Research in seven states, and studies of Tulsa, Boston, and Kalamazoo.) These studies do not directly show lasting impacts of pre-K. But they show much larger immediate impacts of many state and local pre-K programs than are found in the Head Start randomized control trial or the Tennessee randomized control trial.  Based on the studies that show that early test score impacts predict long-term adult earnings effects, there is good reason to think that these state and local pre-K programs will significantly increase adult earnings.

We should also recognize that even if randomized control trials are the “gold standard” for research evidence, natural experiments meet a good “silver standard” that should also be considered in deciding on the research consensus. No one study is perfect in methodology, and therefore we should consider what the bulk of studies show. Furthermore, most studies look just at one program, and therefore if we want to know whether early childhood education in general tends to work, we also need to look at the bulk of studies, rather than just one study of one program.

Like most studies, the Head Start randomized control trial and the Tennessee randomized control trial have some methodological limitations. The Head Start experiment had an unusually large number of members of the control group that participated in some other pre-K program (about half), therefore it is better interpreted as an experimental study of whether Head Start as of 2003-04 was on average better in its test score impacts than the average quality of other pre-K alternatives, including state pre-K programs.

The Tennessee study had large and differential attrition from the treatment group and the control group. For example, in the first cohort, the analyses were based on data from only 46% of the treatment group and 32% of the control group. Although the original treatment and control groups might be similar in unobserved characteristics, it is quite possible that the much smaller group on which the research was largely based may have large differences among the treatment and control group, which raises questions about whether or not the study meets the gold standard. The researchers tried to control for observable differences among the two groups, but obviously it is impossible to statistically control for unobservable differences, which is what a randomized control trial is trying to do, and what a natural experiment is argued to do.  There are some signs that the full sample showed larger impacts on kindergarten retention than the smaller sample after attrition, which suggests that fears of possible biases may be warranted.

In addition, neither Head Start as of 2003-04 nor the Tennessee pre-K program necessarily represent the impact of the highest quality pre-K programs. As mentioned, many regression discontinuity studies of state and local pre-K programs show higher immediate impacts than Head Start (see also Wong et al.). Tennessee’s pre-K program is judged by the National Institute for Early Education Research to spend $2,000 per child less than is thought to be a reasonable amount per child to facilitate quality pre-K services.

Overall, the bulk of the research evidence from many studies has convinced most researchers that high-quality early childhood education can have large and lasting impacts.  The Head Start randomized control trial and the Tennessee randomized control trial do not provide additional evidence that supports the effectiveness of early childhood education. But contrary to Whitehurst and a minority of researchers, these two studies are insufficient to overturn the bulk of the research evidence from multiple studies of a wide variety of programs.

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Why early childhood education can significantly reduce income inequality

President Obama’s State of the Union address Tuesday night is rumored to talk about a variety of measures to reduce income inequality (perhaps reframed as building “ladders of opportunity” for the poor and middle-class), including early childhood education. I thought it useful to review again why early childhood education can be of particular help in boosting the economic prospects of lower income groups, thereby reducing economic inequality.

First, even if pre-K is universally available, the evidence suggests that high-quality pre-K provides a similar dollar boost to future earnings for children from all income classes. But because children from lower-income families tend to have lower baseline future economic prospects, the percentage boost to earnings from universal pre-K is much greater for children from lower-income households.

Second, the evidence suggests that high-quality child care programs and high-quality parenting programs are much more effective in boosting future incomes for children for lower-income families than for other income groups. As a result, it makes sense for child care and parenting programs to be targeted at lower-income groups, as the benefit-cost ratio for these programs will be far greater for these groups.

How much good can early childhood education do to boost income prospects for children from low-income families? Full-day pre-K for one school year at age 4 can boost long-run earnings by 10%.  A more expensive full-time child care and pre-K program from birth to age 5 can boost future earnings for children from lower-income families by 26%. High-quality parenting programs such as the Nurse Family Partnership could boost earnings another 3%.  Therefore, the earnings boost from a comprehensive package of early childhood education programs could be as great as 29%.

I think most people would regard a 29% boost to earnings as a large earnings boost.  Empirically, such an earnings boost would be roughly sufficient to offset the amount that income growth for the lowest income quintile in the U.S. has lagged behind average income growth since 1979.

Why does early childhood education tend to reduce income inequality? Parenting and child care programs provide services that many lower-income families are unable to provide adequately on their own, unlike higher-income families. For pre-K programs, all children benefit from a service that helps promote cognitive skills as well as social skills and character skills in a group setting. But it’s inherently harder to provide the same percentage boost to middle-class earnings from a service delivered with uniform quality to all children, as the baseline earnings for middle-class groups are so much higher.  As writers such as Lane Kenworthy have emphasized, universal public services of high quality for all are inherently redistributive even if they benefit all income groups.

Early childhood education by itself does not solve all the problems of income inequality and limited upward mobility. The broader K-12 system and higher education and training system need reform to be more effective and provide broader access to all. We need to figure out how to revitalize the American system of job creation to make full employment a reality. A variety of measures from higher minimum wages to expanded wage subsidies are needed to increase take-home wages. But greater access to higher-quality early childhood education can help provide all children with the skills they need to take advantage of the opportunities provided by a better educational and economic system.

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Does early childhood education solve all problems? No, but it is a catalytic investment

David Brooks’s New York Times column of January 24, 2014 reflects a common misunderstanding about how to approach difficult policy issues. In discussing how to “expand opportunity for underprivileged children”, he says that we’ve made the following mistake:

“We’ve probably placed too much emphasis on early education. Don’t get me wrong. What happens in the early years is crucial. But human capital development takes a generation. If you really want to make an impact, you’ve got to have a developmental strategy for all the learning stages, ages 0 to 25.”

This is mostly wrong. Early childhood education investments by themselves, with no other change in public policy, make a “real impact”. Abecedarian/Educare child care/preschool from ages 0 to 5 is estimated to raise the future adult earnings of disadvantaged children by over 25%. Perry Preschool raised adult earnings by 19%. Estimates suggest that the adult earnings boost for disadvantaged children from the Chicago Child-Parent Center pre-K program is 8%, from Tulsa pre-K is 10%, and from Boston pre-K is 15%.

Therefore, we have not placed “too much emphasis on early education”. Rather, we have underinvested, because all these early childhood programs have future benefits, not only in increased adult earnings, but in lower crime, lower remedial education costs, and lower social welfare costs, that are many multiples of their investment costs.

It would cost around $30 billion in additional annual spending to offer voluntary universal pre-K to all 4-year olds. It would cost around $60 billion in additional spending to offer all children in poverty under the age of 5 with high-quality child-care and preschool from birth to age 5. In contrast, the latest appropriations bill provides about $1.4 billion in additional annual investments in early care and education. $1.4 billion is clearly a step forward, but in a country the size of the U.S., and given the evidence of the benefits of expanded early investments, it is nowhere near as large as is justified by the empirical evidence.

It is true that full investment in early childhood programs would not solve all problems of poverty and income inequality.  If we interpret Mr. Brooks as just saying that we need to consider a wide variety of policies to tackle the challenges of childhood poverty, how could anyone quarrel with that? We need to consider how to improve K-12 schools, how to improve parenting, how to create more jobs and more income for lower income parents, and so on.

But the art of public policy analysis is finding some way out of the sense of futility that occurs if we believe that no difficult problem can be significantly addressed without doing everything at once. If only comprehensive strategies will make a real difference, then in the real world, complex social problems have no real solution, because policymakers are seldom likely to in one fell swoop adopt a comprehensive strategy.

What we need to find are solutions that play a key catalytic role, which by themselves will have a high bang for the buck, a high benefit-cost ratio. Early childhood education is one such catalytic investment. We then can proceed incrementally, building on success to add other programs and strategies that can make a difference. That incremental strategy of going from one catalytic investment to another is something that policymakers can do, and that has real hope as a political and social strategy for success.

Posted in Early childhood program design issues, Early childhood programs

Public radio broadcast about Jean Jennings Bartik and the other ENIAC programmers

WMUK, the local public radio station in Kalamazoo, did a radio show on January 15, 2014 about my mother, Jean Jennings Bartik (1924-2011). The show was prompted by the recent publication of her memoirs, Pioneer Programmer: Jean Jennings Bartik and the Computer that Changed the World.  The station has posted a short description of the show’s topic, and a link to about a 17 minute broadcast.  The show consisted of an interview with me, and with Kathryn Kleiman of the Eniac Programmers Project, who is nearing completion of a documentary on the ENIAC programmers.

My mother was one of the first six computer programmers, all women, on the ENIAC, which was the computer that in 1946 directly led to the development of the modern computer industry. Her story was ignored for many years, and is still unknown by many. I know that one of my mother’s main motivations in writing the book was so that the story of the ENIAC programmers might help increase the representation of women in computing and other science and technology fields. Role models matter.

My mother’s book is available at Truman State University Press, Amazon, Barnes and Noble Nook, Apple iBook, and a Kalamazoo bookstore, Bookbug. All proceeds from the book will go to support a scholarship for women in science and technology at my mother’s alma mater, Northwest Missouri State University.

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The case for pre-K depends not just on empirical details of studies, but on what you view as plausible given what we know about child development, and on how urgently you view the problem of inequality versus the problem of taxes and deficits

The Cato Institute, a well-known libertarian think tank, sponsored a discussion of research on pre-K on January 7, 2014.  I watched a live stream of the event. The discussion featured George Mason professor David Armor, Brookings Institution researcher Russ Whitehurst, and Georgetown professors Deborah Phillips and Bill Gormley.  Conor Williams provided some coverage of this event.

The discussion was really in part a debate, with Armor and Whitehurst arguing that the research evidence is insufficient to support widespread expansion of pre-K programs, and Phillips and Gormley arguing that the research supported the effectiveness of high-quality pre-K in affecting the life course of disadvantaged children.  The arguments included the following: Armor emphasized what he sees as the deficiencies of the regression discontinuity studies, an argument I have previously discussed. Whitehurst emphasized the statistical insignificance of the Head Start random assignment results. Phillips emphasized what we know about child development in early childhood, and the statistical consensus of pre-K’s effectiveness summarized by the recent report by a group headed by Yoshikawa and Weiland, and which also included Gormley and Phillips. Gormley argued that the regression discontinuity studies were valid, because there is no sign of bias due to attrition in that the treatment and comparison groups are similar in observable variables.

What occurred to me is that the debate over expanding pre-K is in part a philosophical debate, not one that hinges solely on the details of empirical studies. Whitehurst at some point made the statement that the Head Start random assignment experiment showed “no sustained impacts”. Later on, he states that after the pre-K year, there were “no effects”. (Whitehurst previously said something similar in a Brookings post last January:  “There is no measurable advantage to children in elementary school of having participated in Head Start….  Head Start does not improve the school readiness of children from low-income families.”)

That’s not exactly what the Head Start random assignment study shows. What it shows is that the point estimate of the effect of Head Start on cognitive skills is statistically insignificantly different from zero as of third grade.  The point estimates of the effects of Head Start in this study decline by over 70% from the end of Head Start to the end of third grade. The resulting point estimate at third grade would predict that Head Start would improve future earnings by a little over 1%, which is not a trivial amount of money over a lifetime. But we cannot statistically reject the possibility that the true effect might be zero. We also cannot statistically reject the possibility that the true effect might be 2 or 3 times as large.  (Note to wonks: this is using data from the Head Start final impact report to calculate average effect sizes of 0.22 and 0.06 at the end of Head Start and the end of 3rd grade on the PPVT, the WJ III Letter-Word ID test, and the WJ III Math Applied Problems test. These test score effects are then used in conjunction with estimates by Chetty et al. of how test scores affect adult earnings.)

In addition, past studies of early childhood programs, including Perry, the Chicago Child-Parent Study, kindergarten class quality (Chetty et al.), and Head Start itself suggest that test score effects of these interventions often fade, but then the programs still have larger effects on adult outcomes than would be predicted by these faded test score effects. It is certainly possible that this will occur in the Head Start experiment.

Therefore, the Head Start random assignment experiment study is hardly strong evidence in favor of the effectiveness of Head Start, as it was in 2002, in improving third grade outcomes.  On the other hand, given that there is much other empirical evidence in favor of pre-K programs, and even Head Start, and given the statistical uncertainty in these Head Start results, the Head Start random assignment experiment is not strong evidence against the effectiveness of all publicly-funded pre-K.

But how do we interpret these results? One possibility is that we have a strong prior belief that the effect of pre-K programs is zero, either because we are generally skeptical of government intervention, or because we don’t think that academic intervention at age 4 makes sense from a child development standpoint. In addition, perhaps we are concerned about the danger of wasting money on a pre-K program that doesn’t work, which will drive up either deficits or taxes, which might be viewed as adding to our fiscal problems.

Another possibility is that we believe, based on the child development literature, that it is plausible that more time in educational programs at age 4 can make a difference.  We find that there is research evidence from a number of studies that supports that plausible hypothesis, even with test score effects fading. In addition, perhaps we are concerned about the dangers of NOT expanding pre-K funding. Income inequality is a pressing problem that is difficult to address. Developing human capital seems like a key way to address income inequality. Adding more early learning time is a straightforward policy that addresses human capital development. We know how to add high-quality early learning time, and we have done so in a number of state and local areas.  Failure to do so may have a large opportunity cost.

In other words, is the greater danger from expanding a pre-K program that doesn’t work? Or is the greater danger from not expanding pre-K programs that could make a major difference to many children’s future?

There will always be some policy uncertainties. It is more difficult to precisely estimate long-run effects of programs than short-run effects, and more difficult to precisely estimate aggregate effects of programs than effects on a specific group of individuals. Random assignment experiments will always be scarce because they are difficult and expensive to run.

How we resolve policy uncertainty is a choice. That choice is based in part not on the empirical evidence, but on our prior beliefs about child development, government intervention, and the relative dangers of excessive government spending versus increased income inequality.

One way to reduce the risk of doing the wrong thing is to expand pre-K, but to do so in a way that maximizes the probability that the intervention is high quality. This suggests that we should err on the side of spending more per child, and that we should be doing a great deal of monitoring of quality and results in pre-K programs.

Posted in Early childhood program design issues, Early childhood programs | 2 Comments