Students walk to classes at Dartmouth College in Hanover, N.H., in 2001. (Jim Cole/Associated Press)

Craig Sutton is an associate professor of mathematics at Dartmouth College.

As winter approaches in Hanover, N.H., the admissions season at Dartmouth College is in full swing. By the start of the new year, the college’s admissions office will receive roughly 20,000 applications from talented scholars vying to join the Class of 2020. By spring, Dartmouth’s incoming class will be a diverse community of students with different intellectual passions, native languages, religions and political leanings. However, like its counterparts at other Ivy League institutions, this class will fail to be diverse in at least one important respect: socioeconomic status. Surprisingly, this lack of economic diversity arises from a well-intentioned policy — need-blind admissions — acting in combination with noninclusive recruiting networks.

According to recent data, almost 60 percent of the Dartmouth student body comes from households in the top 6 percent of the national income distribution (those earning at least $200,000 a year), while about 11 percent is drawn from the bottom 40 percent (earning less than $50,000). That is, for every six Dartmouth students from the wealthiest U.S. households, there is one from a low-income household.

At first glance, there might seem to be a simple explanation for this: High-income families must produce many more high achievers than low-income ones. But a 2013 study by Stanford University economist Caroline M. Hoxby and Christopher Avery of Harvard University’s Kennedy School of Government suggests the difference between the two groups is much smaller than you would think. They estimated that in 2008, households in the top 25 percent of the income distribution accounted for 34 percent of high achievers (high school seniors with at least an A-minus grade-point average and scoring at or above the 90th percentile on the SAT or ACT), whereas the bottom quartile of households accounted for 17 percent of high achievers. In other words, for every two high-achieving students from the top quartile of the income distribution, we should expect one high achiever from the bottom.

Why are low-income high achievers grossly underrepresented at elite colleges?

Part of the problem is that many low-income high achievers apply only to less selective colleges, leading to what Hoxby and Avery call “undermatching.” They find that low-income high achievers tend to be geographically isolated from other high achievers, are less likely to encounter teachers and mentors who attended elite colleges and often live in rural school districts rarely frequented by admissions officers of elite institutions. Additionally, low-income students often don’t realize that they would probably pay far less at a prestigious institution than a less-selective one.

So, how can prestigious universities achieve increased socioeconomic diversity?

Many of the most selective institutions use need-blind admissions policies, which prohibit coordination between admissions and financial-aid offices. Need-blind admissions combined with outreach programs — primarily focused on urban areas — initially boosted efforts to diversify elite campuses. But with admissions officers able to identify low-income high achievers only through proxies such as Zip codes and the content of personal essays, recent decades have witnessed stagnation. As long as the number of applications from high-income high achievers continues to dwarf those of their low-income counterparts by a ratio that can range from 8-to-1 to as much as 15-to-1, according to Hoxby and Avery, there appears to be little more that a need-blind system can do to improve things.

There is a debate over whether the recently announced Coalition for Access, Affordability, and Success formed by more than 80 highly competitive schools will eventually succeed in building more-inclusive recruiting networks. In the meantime, elite universities can advance socioeconomic diversity by revising their admissions policies.

Every year, many remarkable students are wait-listed by prestigious universities and ultimately denied admission. Among them are a significant number of low- and middle-income high achievers. If the blinders were removed before the wait list was formed, admissions officers could adopt a “need-affirmative” policy favoring high-achieving low- and middle-income students to create a more balanced and inclusive campus.

Critics might call need-affirmative admissions unfair because it would penalize some applicants for being too wealthy. However, this would hardly be the only “penalty” embedded in the admissions process.

“Athlete-affirmative” admissions programs at elite institutions allow coaches to fill out their rosters with talented athletes of their choosing, a level of influence not enjoyed by any academic department. “Legacy-affirmative” admissions programs aim to foster loyalty to an institution by favoring the descendants of alumni. The benefits of achieving a socioeconomically diverse student body make a need-affirmative policy at least as compelling as athlete-affirmative and legacy-affirmative admissions.

The lifeblood of an elite university is its ability to assemble a critical mass of young scholars possessing an extraordinary level of intellectual passion and creativity. This goal will remain elusive if we continue to lean so heavily on a sliver of U.S. households to populate elite campuses. By adopting a need-affirmative admissions policy, elite institutions can immediately increase the number of low- and middle-income students on their campuses and position themselves to serve as wellsprings of innovation and engines of opportunity for an increasingly diverse nation.