New research delivers a crushing blow to advocates of “free” college: Expanding access to higher education won’t do anything to reduce income inequality.

While it’s true that students who graduate from college do tend to earn more money throughout their careers than those who don’t, low-income students don’t get the same earnings boost as students from high-income families.

Economists at the UpJohn Institute studied low-income families, classified as those with an income below 185 percent of the federal poverty line, which ends up being around $45,000 for two parents and two kids, and found that a college degree could increase their lifetime earnings by 71 percent.

For those earning above that threshold, lifetime earnings increased by a much larger 136 percent.

“The average college graduate from a low-income family earns as much at career peak as the average college graduate from a higher-income family at career beginning,” the authors wrote.

The Brookings Institute illustrated the results in the chart below.

Author Brad Hershbein offered several possible explanations for this trend, including family resources available during childhood, the location where one grew up, and the different colleges that low- and high-income students attend. There is also the "network effect," or connections that students from wealthy families tend to have that are often highly influential in expanding career opportunities. Hershbein and his colleagues plan to investigate these trends further in the coming months.

The decision to go to college is still a good one for low-income students, and will result in higher lifetime earnings, but it won’t necessarily do anything to equalize earnings. Therefore, offering low-income students tuition-free college is not a viable solution to rising income inequality.

These results run counter to conventional wisdom and ideas that have taken hold of the Democratic Party in 2016. Senator Bernie Sanders led the effort for tuition-free college, energizing his primary campaign and capturing votes from thousands of young people. Different versions of the idea are now championed by Hillary Clinton and Democrats down the ballot.