Every year, hundreds of thousands of workers from abroad come to the United States to temporarily fill jobs in a number of occupations, including farm labor, landscaping, hospitality and seafood processing, as well as information technology jobs or to teach at U.S. universities and grade schools. They come through a virtual alphabet soup of temporary foreign worker programs which are distinguished by different “nonimmigrant” visa classifications, each having their own distinct purpose and history. The most common nonimmigrant visas that authorize employment are the H-2A, H-2B, H-1B, J-1, L-1, A-3, G-5, F-1/Optional Practical Training (OPT), and B-1 visa classifications, but also important are H-1B1, O-1, O-2, E-2, E-3, P-1, P-2, Q-1, and TN visas. The workers themselves, who hold nonimmigrant visas, are commonly referred to as guestworkers and are allowed to remain and work in the country for a limited period of time, depending on the terms of their specific visa.

Over the years, countless cases of abuse and exploitation of guestworkers have come to light and been reported on by the media. The abuses are usually carried out by employers or the labor recruiters who connect guestworkers to their jobs and employers, for a fee. Some of the abuses are extreme and amount to human trafficking: they have been compared to slavery by Buzzfeed and the Southern Poverty Law Center and described as “creating an underground system of financial bondage” by the Center for Investigative Reporting. None of these labels are an exaggeration.

Unfortunately, little else is known about how these guestworker programs operate, despite the fact that hundreds of thousands of guestworker visas are issued every year. That makes it difficult to craft rational policy solutions to improve how the programs are managed and to ensure that the labor standards of guestworkers—and of Americans who work in major guestworker occupations—are protected. The dearth of information also results in an outsized role for corporate interest groups that spend millions lobbying to expand and deregulate guestworker programs, because it is difficult for lawmakers to verify claims about how guestworker programs impact the economy, businesses, and the labor market.

That’s why the Visa Transparency Anti-Trafficking Act, a new piece of legislation introduced today in the House by Reps. Lois Frankel (D-Fla.), David Schweikert (R-Ariz.), Ted Deutch (D-Fla.), and Jim Himes (D-Conn.), and in the Senate by Sen. Richard Blumenthal (D-Conn.), is so important. The Act would create a uniform system for reporting data that the government already collects on work visa programs and require making that information available to the the public, non-governmental organizations, researchers, and lawmakers. Because the government already possesses a vast amount of data on guestworker programs and temporary visas, the bill does not require the government to collect much more or to impose new burdens or requirements on employers. It would simply provide increased access to this information. That may seem like a small step, but it would go a long way to bringing a much-needed dose of transparency to our immigration system and drastically improve the quality of public debates surrounding temporary foreign worker programs.

There are three things to know about nonimmigrant visas. First, guestworkers must depart the country after the visa expires, because nonimmigrant visas almost never lead to a permanent immigrant status (i.e., lawful permanent residence) or citizenship. Second, each visa is owned and controlled by a single employer, which means that if a guestworker gets fired, he or she becomes instantly deportable. As a result, this also means that when things go wrong on the job or if an employer breaks the law or treats a guestworker unfairly, the employee has a strong incentive to keep quiet and not complain to the boss or the authorities. And third, reports in the media, from think tanks, and from government auditors have highlighted for years how guestworker programs have facilitated labor and sex trafficking. Organizations like Polaris that work to end modern-day slavery and human trafficking keep statistics on how many of the cases they encounter involve a nonimmigrant visa: 40 percent of the calls to their victim hotline from August 2014 to July 2015 referenced nonimmigrant visas.

Given the prevalence of guestworker programs and their notoriety, it would be reasonable to assume that basic facts about the programs are well known, including, the number of guestworkers currently employed in the U.S. labor market, the occupations those guestworkers are employed in, or how much they get paid. But such an assumption would be mistaken. In fact, the government says in its report on the “nonimmigrant resident population” that the number of guestworkers in the country at any given time can only be “estimated, as opposed to measured” because key data are lacking. While no one knows what the exact number is, there is evidence suggesting that guestworkers probably make up about one percent of the U.S. labor force.

And when it comes to basic information about the cities and states where guestworkers work, the jobs they do, and how much they earn, it is nearly impossible to get any useful information because the government doesn’t publish much of what it collects. The only way to get it is to file a Freedom of Information Act (FOIA) request and hope that the government grants the request. The good news is that the government collects quite a lot of this information from employers who hire guestworkers. The bad news is that they keep most of it on paper files—rather than electronically—which means that even if a FOIA request is granted, the government will only release the parts that have been transferred to an electronic format. For most work visa classifications, this is problematic because the government usually does not electronically record the work locations or salaries of guestworkers. But even when the government actually grants the request, has the data, and hands it over—which occurred recently on a FOIA request I was involved with for H-1B wage data from United States Citizenship and Immigration Services, which took an entire year to process—the government will redact the information and claim a privacy exemption.

Such record-keeping practices are not consistent with the standards of a modern, developed country. The Obama administration’s practice of not storing electronically and not regularly releasing basic-but-essential data about immigration and the labor market is also inconsistent with President Obama’s claim that his administration is the most transparent in history.

If Congress passes and the president enacts the Visa Transparency Anti-Trafficking Act, the law would put the American immigration system on the path to modernization and transparency, and perhaps ultimately, credibility. But without it, policymakers and the public will lack the evidence they need to evaluate the impact of guestworker programs on the economy and to know whether guestworkers are being paid fairly or are instead being exploited to undercut U.S. wage standards. In addition, the outreach and prevention efforts of anti-trafficking advocates will continue to be hindered if they don’t know which industries hire guestworkers and where they are located. Transparency and fairness are bipartisan concerns; that’s why members of Congress from both parties and on all sides of the immigration debate should come together to support the Visa Transparency Anti-Trafficking Act.