Since its introduction in 1996 as Basic Pilot, E-Verify remains the easiest way for employers to determine if their workers are eligible to work legally in the United States. A 2016 study confirmed what many have known for years: The E-Verify system is remarkably effective at deterring illegal immigration.

In their article "Do State Work Eligibility Verification Laws Reduce Unauthorized Immigration", researchers Pia M. Orrenius and Madeline Zavodny found that "having an E-Verify law reduces the number of less-educated prime-age immigrants from Mexico and Central America — immigrants who are likely to be unauthorized — living in a state." They studied the direct effect that the adoption of E-Verify has on the illegal alien population. They focused on Alabama, Arizona, Georgia, Mississippi, North Carolina, South Carolina, and Utah — all states that adopted E-Verify policies.

The researchers constructed their test by using data collected by the U.S. Census' American Community Survey for the years 2005-2014. Although the ACS survey does not ask for immigration status, by using age, education, country-of-birth, and citizenship status the researchers could create an accurate representation of what the unlawfully present population looks like. Specifically, they defined illegal aliens as foreign-born aged 20-54 who have at most completed high school, are from Mexico and Central America, and are not U.S. citizens.

The effects that E-Verify has on the illegal population are astounding. Orrenius and Zavodny found that the number of newly arrived aliens (those most likely to come for employment) fell by nearly 50 percent when a state implemented a mandatory E-Verify law. That is a direct testament to the powerful effect that verification laws have on the ability of illegal aliens to work. The effects were particularly profound in Arizona, where the researchers found an exodus of alien workers following the implementation of mandatory E-Verify in 2008.

The study unveiled a number of other pertinent findings as well. One was that E-Verify had a greater negative effect on the presence of illegal workers than other related efforts, indicating that workplace enforcement is the surest way to reduce the population of illegal workers in a given state. The specific example provided was the 287(g) program that allows for local law enforcement to wield authority for immigration enforcement within their jurisdictions. The study did not report on the effectiveness of the program (arrests, less crime, etc.) but did report that the presence of 287(g) was not as effective a deterrent to the illegal population as E-Verify was.

They also found that the deterrent effect of E-Verify was only present when E-Verify was mandated for all employers. There was no effect on the immigrant population when only government employers or government contractors had to use E-Verify. They write that "the results indicate that E-Verify requirements for government employees and government contractors have relatively little effect on the number of likely unauthorized immigrants or less-educated U.S. natives in a state. This is not surprising since relatively few unauthorized immigrants are directly affected by those laws."

Their study indicates that E-Verify is one of the most important enforcement tools available to states that wish to reduce their illegal alien populations. Research shows that most illegal migration is for economic reasons, and that the adoption of E-Verify and other worksite enforcement measures effectively blocks illegal aliens from procuring employment, thereby preventing many from settling down in the United States. Faced with mandatory E-Verify, the study shows that many aliens either returned to their home countries or traveled to other states that did not have employment verification regulations.

E-Verify is a powerful tool that could have a significant effect on illegal immigration if properly implemented nationwide. A universal E-Verify requirement has been included in a number of bills introduced in this congressional session, including the RAISE Act, the Legal Workforce Act, and the American LAWS Act. As Congress debates how to reform our broken immigration system, they should heed the closing remarks of the study: "[P]olicymakers should consider adopting [E-Verify] if they hope to reduce the number of unauthorized immigrants to the USA."