One of the most often-cited reasons to oppose a path to citizenship for undocumented immigrants is the idea that by creating one, we’ll just encourage more illegal immigration in the future. The concept is that if you agree to give legal status to illegal immigrants, it will put an idea into the heads of the potential illegal immigrants of the future that there will be a similar program after they arrive for them to take advantage of, and therefore they will perceive a significant added incentive to immigrate illegally to America. This is a common argument — for instance, one member of a group of eight House members who are allegedly working on a compromise bill, Raul Labrador, is professing concern about this supposed problem. Politically, this argument makes it look like denying current undocumented immigrants a path to citizenship isn’t about punishing them — instead, it’s about the future, because adopting such a policy could lead to bad consequences down the road, and serious people should be concerned about this.

The problem with this argument is that there’s no evidence for it.

Most Americans would have no trouble identifying the primary reason that people immigrate illegally to our country: Most of these migrants want to take advantage of the huge wage differences that exist between their home countries and America, but they’re low-skill workers who either aren’t eligible to immigrate here legally or who encounter extremely long waits. At first glance, it may seem plausible that enacting even a limited path to citizenship may lead them to think there are potentially fewer negative consequences for them to come, tipping the scales toward them crossing the border illegally. But when you think about the strong economic reasons they have for migrating, along with the dangers they face when they try to do so, then it becomes pretty apparent that speculation about the future policy decisions of the U.S. government is pretty low down on their list of factors.

The research bears this out. We actually have a pretty good test case for this: The 1986 Simpson-Mazzoli legislation (IRCA), which contained the much-discussed “amnesty” for 3 million people illegally in the United States at that time. The proposals now would require applicants to go through a longer and much more rigorous process. (It is not really an “amnesty.”) The 1986 legalization has actually been the subject of several scholarly studies that looked for its impacts on future illegal immigration.

A useful review of the evidence is provided by a 2003 journal article by the two immigration economists Pia Orrenius and Madeline Zavodny. When you review the data, the gist is that the 1986 amnesty had no real effect on levels of illegal immigration from Mexico, either encouraging it or discouraging it. In their words:

Apprehensions declined immediately after the passage of IRCA but then returned to normal levels during the amnesty filing period and thereafter. These results have several implications. Because we found that apprehensions did not rise during the filing period, as would be expected if people migrated to the United States to apply for the program fraudulently, it appears that amnesty programs do not encourage undocumented immigration, as some critics of amnesty programs have charged. If anything, IRCA reduced the number of undocumented immigrants in the short run, perhaps because potential migrants thought that it would be more difficult to cross the border or to get jobs in the United States after the law was passed. An amnesty program also does not appear to have encouraged undocumented immigration in the long run in the hopes of another amnesty program; we did not find a significant difference between apprehensions before IRCA was created and after the program expired. However, it also appears that IRCA failed to discourage undocumented immigration in the long run.

The authors list some minor caveats to this data, and it’s worth noting that the authors deal with rather coarse data about border apprehensions rather than individual-level data. That’s not ideal. Overall, though, the story of the numbers is pretty clear: The 1986 legalization didn’t prevent illegal immigration from that point on (it’s unclear why it might), and illegal border-crossing seemed to pick up after a brief drop. But there’s no evidence that speculation about a future legalization program encouraged more people to immigrate legally after the 1986 was either debated or passed. What was significantly associated with increased apprehensions at the border (the usual proxy for estimating illegal cross-border traffic) over the long run were enforcement and economic conditions. But, as the post-IRCA policy regime lacked both truly improved enforcement and improved legal channels, passing the law didn’t seem to make an impact either way on the volume of illegal immigration. None of the other pieces of research cited by these two authors concludes that, based on the data, the 1986 legalization caused an increase in illegal immigration.

On the other hand, the arguments that “amnesty” (or a path to citizenship) would prompt more illegal immigration never refer to any numbers, data, or evidence — at least not that I’ve ever seen. The only statement I’ve seen that refers to any numbers at all is from Lamar Smith, the hardline congressman from Texas, who cites Zogby polls of Mexicans who think that legalization might lead to more illegal immigration to the United States. Clearly, though, this isn’t exactly the same thing as observing behavior. In fact, as evidence, it’s extremely flimsy. Maybe that’s why proponents of this argument don’t ever seem to bother with any numbers at all.

It’s hard to avoid the conclusion that the “legalization leads to more illegal immigration” argument utterly lacks any supporting evidence. If anyone knows of a study that finds otherwise, please let me know, and I’d be happy to reconsider that statement in light of it.

People who keep track of the politics of immigration shouldn’t mistake our own interests for those of a group of unskilled workers choosing whether to try to immigrate unlawfully. Remember: speculating about policies the U.S. federal government might enact is what people who work in the DC media or for immigration think tanks do to secure their livelihoods; making decisions based on economic conditions and perceived costs of migrating is what low-skill potential migrants do to secure theirs.