| 摘要 | Economic diversity at America’s colleges and universities is a hot issue these days. The U.S. News College Rankings recently updated its methodology to measure how well institutions are serving low-income students. Six Democratic senators complained the changes didn’t go far enough and demanded the inclusion of an “exclusive metric assessing the access a college…provides to historically underrepresented students.” Other members of Congress have proposed bills to reward colleges for enrolling more low-income students, while some policy experts want to give tax relief to schools with more economic diversity.
Many of these ideas stem from a 2017 paper by economist Raj Chetty and his colleagues at the Equality of Opportunity project. The paper uses comprehensive tax data to assign each college a “mobility report card,” which measures how well the school serves students from the bottom 20% of the national income distribution. The project inspired a widely-read New York Times article presenting many of America’s top colleges as bastions of the rich and privileged.
Now, many politicians and commentators want to use Chetty’s methodology to judge American colleges, and punish those with unacceptably low shares of students from the bottom of the income ladder. But a new analysis from economists Caroline Hoxby and Sarah Turner suggests we should hit pause on those efforts.
Hoxby and Turner note that most colleges can’t simply enroll whichever students they want. The vast majority of students, particularly those who attend public colleges, end up going to an institution within their home state. Lower tuition for in-state students and the familiarity of nearby schools keeps most students attending colleges close to home, which in turn means that the student body of the typical public college consists mostly of in-state students.
When selecting which students to admit, the typical college has to choose from a pool of mostly own-state residents, not from the national population. This complicates the Chetty methodology of applying a standard based on the national income distribution to colleges in fifty diverse states. Asking how well a college is serving students from the bottom 20% of the national distribution tells us very little about how that college is serving disadvantaged students from its own state.
Hoxby and Turner expose this problem by analyzing the student population at the flagship public university in each state. Chetty’s preferred measure of economic diversity tells us that the University of New Mexico-Albuquerque is one of the most economically diverse schools in the country, with more students from the bottom 20% of the national income distribution than any other state flagship.
But New Mexico is also one of the poorest states in the Union, with a median household income more than $10,000 below the national figure. Thus, the University of New Mexico naturally enrolls plenty of low-income students. To adjust for this, Hoxby and Turner compare the income distribution of the school’s student body to the “pool” of students from which it is likely to draw. In other words, the authors ask how well each flagship university is serving students from the bottom of the income distribution of college-ready students in its own state.
Ranking the schools on this measure rather than the crude national one, Hoxby and Turner show that the University of New Mexico ranks a disappointing 34th out of 50 states. When taking the state population into account, the school is not quite the standout example of economic diversity it looks like at first.
But other schools which previously seemed elitist now look egalitarian. One example is the University of Wisconsin-Madison, which ranks 36th out of 50 on the national measure of economic diversity. But Wisconsin is a much richer state than New Mexico, and also a more equal one, with the result being that it has fewer poor students for the state university system to enroll. But the University of Wisconsin-Madison serves the state’s few poor students quite well, ranking sixth out of 50 on Hoxby and Turner’s adjusted measure of economic diversity.
A policy to reward or punish colleges based on how their student bodies stack up against the national income distribution may inadvertently penalize schools which are actually doing quite a good job serving disadvantaged students, considering the hand they’ve been dealt. Though there are many ways for colleges to improve, the share of students they enroll from the bottom 20% of the national distribution is partially out of their control.
More importantly, the Hoxby-Turner analysis reminds us that certain statistics may look airtight at first glance, but reveal severe limitations once one considers the broader context. Policymakers who want to use the heavy hand of government to promote economic diversity at American colleges would do well to remember this. |
