摘要:We review what is known about Head Start¡¯s impacts on children and argue that the program is likely to
generate benefi ts to participants and society as a whole that are larger than program costs. Our conclusions differ
from those in some previous reviews because we use a more appropriate standard to judge program effectiveness
(benefi t-cost analysis), draw on a body of new evidence for Head Start¡¯s long-term effects on early cohorts of
participating children, and discuss why common interpretations of a recent randomized experimental evaluation
of Head Start¡¯s short-term impacts may be overly pessimistic. Estimating the long-term benefi ts of Head Start
for recent participants necessarily requires a number of assumptions. But we believe there is a plausible case that
short-term effects on achievement scores of .1 to .2 standard deviations might be large enough for Head Start to
pass a benefi t-cost test. Data from the experiment imply that Head Start enrollment ¨C as distinct from assignment to
the experimental treatment group ¨C usually generates impacts of at least this magnitude. While, in principle, there
could be more benefi cial ways of deploying Head Start resources, the benefi ts of such changes remain uncertain and
there is some downside risk. There is a growing scientifi c consensus that a variety of early childhood interventions
generate benefi ts in excess of costs at current levels of spending, which suggests the value of increased spending
in this area. However there remains considerable uncertainty about what form any additional investment should
take. Additional government funding to support rigorous research to identify the relative strengths of Head Start
and its alternatives, as well as the critical ¡°active ingredients¡± in these programs that most effectively produce
short- and long-term developmental benefi ts, would be a particularly high value-added activity.