More than any other group, black job applicants are being turned away by U.S. companies under the implicit assumption that they are using illegal drugs, according to a new study published by the National Bureau of Economic Research (NBER).

The study’s author, University of Notre Dame economics professor Abigail Wozniak, looked at how hiring practices differ between states with laws that incentivize or encourage drug testing and states with laws that limit or do not require such testing. She found that pro-testing legislation has a “large” and positive effect on black employment and wages, especially among low-skilled black men.

As the chart below shows, enacting pro-drug testing laws improves the share of blacks working in what Wozniak terms high-testing industries, while leading to a decrease in the share of whites working in such industries.

In states that enact anti-testing laws, the opposite proves true: Limiting drug testing appears to hurt black applicants much more than it hurts whites.

The findings imply that companies in states without pro-testing laws are, subconsciously or not, assuming black job applicants are guilty of using illegal drugs until proven innocent. In Wozniak’s opinion, drug testing can therefore help “non-using blacks to prove their status to employers, even as the drug war linked blacks with drug use in the popular imagination.”

“A common assumption is that the rise of drug testing must have had negative consequences for black employment,” Wozniak writes. “However, contrary to what one might expect, the rise of employer drug testing may have benefited African-Americans.”

But in a phone interview with The Huffington Post, Wozniak cautioned against interpreting the study as proof that employers are explicitly discriminating against black applicants.

“The results don’t look like what you would call typical old-school racism,” Wozniak told HuffPost. “The research in the paper suggest that the bias is coming in more subtle ways.”

“Instead of looking really hard at every applicant, they [employers] have these impressions that they go by," she continued. "Testing gives them a rule of thumb that avoids this bias.”

That “rule of thumb” appears to help. A lot. In fact, Wozniak found pro-testing laws increase the share of low-skilled, black men working in high-testing industries by up to 30 percent and raise their wages by 12 percent compared to anti-testing states.

Enacting no laws hurts black candidates too, according to Wozniak's study. When compared to low-skilled, black men in states with no drug testing laws, low-skilled, black men in pro-testing states saw their employment increase by 7-10 percent and their wages increase by 3-4 percent.

Tamar Todd, a senior staff attorney at the Drug Policy Alliance, compared the findings of the study to the disproportionate incarceration rates among black Americans because of the war on drugs. Multiplestudies have found that while blacks and whites in the U.S. tend to use drugs at similar rates regardless of race, blacks are much more likely to be arrested for drug-related offenses.

“It reflects what we know,” Todd said of the new study.

Racial bias has long been known to play some role in the job application process. In 2003, two NBER research fellows published a paper finding that resumes with names that occur frequently among the white population were much more likely to lead to callbacks for an interview than resumes with names that occur more frequently among the black population.

But Maurice Emsellem, a program director at the National Employment Law Project focusing on criminal records and employment, said the answer is not to require more drug testing, but rather "to take aggressive action to limit racial bias in the hiring process."

When companies don’t test for drugs, who is likely to get the job instead of a passed-over black applicant? According to Wozniak’s research, it’s white women. In fact, women as a whole actually appear to be the big losers of pro-testing legislation.

“[T]he impacts of pro-testing legislation are uniformly negative,” Wozniak writes. “High testing industry employment, large firm employment, and benefits coverage all decline for women by about 1.5 percentage points.”

According to 2007 data from the Department of Health and Human Services, 42.9 percent of employees reported that tests for illicit drug or alcohol use occurred at their place of employment during the hiring process.

Wozniak hopes that as a result of her study, people will begin to see drug tests and other available job-search tools not as inhibitors to minorities, but rather as ways for employers to fight their own implicit racial biases.

“Many people may assume that drug testing is harmful and that it makes getting a job more difficult,” Wozniak said. "But I think the evidence is strong that that’s not true for African-Americans.”