Ashenfelter and Rouse Twinsburg Data

In "The Varied Economic Returns to Postsecondary Education: New Evidence from the
Class of 1972", an article recently published in the Journal of Human Resources (Volume 28,
no. 2, pp. 365-382), Norton Grubb reaches two main conclusions: (1) students who enroll in
two-year colleges without completing degrees earn no more than comparable high school
graduates; and (2) degrees from two-year colleges and vocational and technical institutes only
indirectly lead to higher earnings by providing students with access to jobs in which they can
accumulate experience and on-the-job training (i.e., access to "careers" instead of "jobs"). Given
that roughly half of those entering college today do so at community colleges and that roughly
a fifth of federal Pell Grant subsidies are spent at these institutions, such results are quite
provocative.
However, in this comment we show that several of the variables used in Grubb’s paper
are severely mismeasured and that, when they are corrected with reasonable alternatives, his
conclusions no longer receive empirical support. On the contrary, even those who enter but fail
to complete degrees at community colleges do seem to earn significantly more than similar high
school graduates. Further, controlling for work experience has relatively little effect on the
estimated returns.

Many argue schools that serve inner-city and rural children are in “crisis.” This paper
reviews the best available evidence on the effects of class size and school vouchers. Results from
the Tennessee STAR experiment suggest smaller class sizes improve achievement, particularly for
inner-city and minority children; results from the New York City voucher experiment and the
Milwaukee Parental Choice program suggest there may be small achievement gains in mathematics
for the African-American and Hispanic children who use vouchers. Although the reason of the
achievement gains is unknown, one candidate is the smaller class sizes in the private schools.

In a recent, and widely cited, paper, Ashenfelter and Krueger (1994) use a new sample of identical
twins to investigate the contribution of genetic ability to the observed cross-sectional return to schooling.
This paper re-examines Ashenfelter and Krueger’s estimates using three additional years of the same twins
survey. I find that the return to schooling among identical twins is about 10 percent per year of schooling
completed. Most importantly, unlike the results reported in Ashenfelter and Krueger, I find that the within-
twin regression estimate of the effect of schooling on the log wage is smaller than the cross-sectional
estimate, implying a small upward bias in the cross-sectional estimate. Ashenfelter and Krueger’s
measurement error corrected estimates are insignificantly different from those presented here, however.
Finally, there is evidence of an important individual-specific component to the measurement error in
schooling reports.

We study the effects of a change in financial aid policy introduced by a Northeastern
university in 1998. Prior to that time, the university s financial aid packages for lowincome
students consisted of grants, loans, and campus jobs. After the change, the entire
loan portion of the package for low-income students was replaced with grants. We find
the program increased the likelihood of matriculation by low-income students by about 3
percentage points, although the effect is not statistically significant. The effect among
low-income minority students was about twice that size and statistically significant at the
10 percent level.

Some argue that a high union wage premium and the industrial council system are important causes
of inflexibility in the South African labor market. We estimate union premia on the order of 20 percent for
African workers and 10 percent for White workers. We also find that African nonunion workers who are
covered by industrial council agreements receive a premium of 6-10 percent; the premium is positive but not
statistically significant for Whites. In addition, although the union gap is smaller inside of the industrial
council system than outside of the system for Africans, the total union premium for union members covered
by an industrial council agreement is similar to the union premium outside of the industrial council system.
Among Africans, the industrial council and union wage gaps are largest among low wage workers.

Although women are underrepresented in the field of economics, many people see little
need for intervention, arguing that women are inherently less interested in economics, or are less
willing or able to acquire the math skills needed to do well in the subject. At the same time,
others support active efforts to increase the number of women in the field, pointing to other
possible causes of their current underrepresentation. These people argue, for example, that
women are deterred from entering the field because of a lack of female role models, or that
women are discouraged by an unappealing classroom environment. This study attempts to
assess these hypotheses. We examine the factors that influence undergraduate students’
decisions to become economics majors by analyzing a survey of students in the introductory
economics course at Harvard University as well as data on an entire class of students from
Harvard's registrar.
We find that although women in the introductory economics course at Harvard tend to
begin the course with a weaker math background than men, math background does not appear
to explain much of the gender difference in students’ decisions about whether to major in
economics. The class environment and the presence or absence of role models also do not
explain much of the gender gap. On the other hand, women do less well in economics relative
to their other courses than men do, and controlling for this difference in relative performance
significantly diminishes the estimated gender gap. An economically large, but statistically
insignificant, difference between sexes in the probability of majoring in economics remains,
however. This remaining gender gap may be due to differing tastes or information about the
nature of economics. As evidence, we find that women who were considering majoring in
economics when they began introductory economics were about as likely to choose economics
as were men.

In the 1970s, the American Economic Association (AEA) was one of several professional associations to launch a summer program with the goal of increasing racial and ethnic diversity in its profession. In this paper we estimate the effectiveness of the AEA’s program which, to the best of our knowledge, is the first to rigorously study such a summer program. Using a comparison group consisting of those who applied to, but did not attend, the program and controlling for an array of background characteristics, we find that program participants were over 40 percentage points more likely to apply to and attend a PhD program in economics, 26 percentage points more likely to complete a PhD,and about 15 percentage points more likely to ever work in an economics-related academic job. Using our estimates, we calculate that the program may directly account for 17-21 percent of the PhDs awarded to minorities in economics over the past 20 years.

In this paper I review the existing evaluations of the effect of the Milwaukee Parental Choice
Program on student achievement. Two of the three existing papers report significant gains in math for the
choice students and two of the three studies report no significant effects in reading. I also extend the analysis
to compare the achievement of students in the choice schools to students in three different types of public
schools: regular attendance area schools, city-wide (or magnet) schools, and attendance area schools with
small class sizes and supplemental funding from the state of Wisconsin (“P-5” schools). The results suggest
that students in P-5 schools have similar math test score gains to those in the choice schools, and students
in the P-5 schools outperform students in the choice schools in reading. In contrast, students in the city-wide
schools score no differently than students in the regular attendance area schools in both math and reading.
Given that the pupil-teacher ratios in the P-5 and choice schools are significantly smaller than those in the
other public schools, one potential explanation for these results is that students perform well in schools with
smaller class sizes.

The economics profession includes disproportionately few women and members of historically
underrepresented racial and ethnic minority groups, relative both to the overall population and to
other academic disciplines. The relative lack of women, African Americans, Hispanics, and
Native Americans within economics is present at the undergraduate level, continues throughout
the academy, and is barely improving over time. In this paper, we present data on the presence
of women and minority groups in the profession and offer an overview of current research on the
reasons for the imbalance, highlighting that implicit attitudes and institutional practices may be
contributing at all stages of the pipeline. We review evidence on how diversity affects
productivity and conclude that the underrepresentation likely hampers the discipline,
constraining the range of issues addressed and limiting our collective ability to understand
familiar issues from new and innovative perspectives. Broadening the pool from which
professional economists are drawn is not just about fairness; it is necessary to ensure the
profession produces robust and relevant knowledge. We propose remedial interventions along
with evidence on effectiveness, identifying several promising practices, programs, and areas for
future research.