The welfare magnet hypothesis was developed in the late 1990s by George Borjas, a Harvard economist and a major influence on right-of-center immigration policy. He reasoned that people arriving in the United States would respond to welfare incentives differently than native-born citizens or already settled immigrants. New immigrants need to make a choice about where to live, making welfare generosity more salient to them than to residents for whom moving would be an expensive, difficult hassle. Lo and behold: “Immigrant welfare recipients are indeed more heavily clustered in high-benefit states than the immigrants who do not receive welfare, or than natives.”

Immigrants were particularly attracted to California, Borjas found. But was that because the state offered the second-most-generous welfare benefit package at the time? Or because many of those immigrants were refugees placed in California by the agencies sponsoring them? Or because of California’s location on the Mexico border? Or because it had such a strong economy and significant job opportunities? Or because of its generally immigrant-friendly politics? Or because of the prevalence of speakers of Spanish and other languages? Or because many new, lower-income immigrants had social ties to the state? Borjas said he detected strong suggestive evidence that welfare generosity was at work, but never proved causation.

That might be because there was nothing to prove: Welfare is just not that strong a magnet. The Clinton administration’s 1996 welfare-reform law created a natural experiment demonstrating this fact. The bill barred immigrants from receiving cash welfare, but some states opted to use their own funds to provide it. If those benefits were a big draw, more single-parent families would have headed to the states offering them. But that did not turn out to be the case. Another influential study looked at poor single women with children moving across state lines, and found much the same: “We find little evidence indicating that welfare-induced migration is a widespread phenomenon.”

Sociological studies and surveys of immigrants help illuminate why: People tend to move for jobs and social networks, more so than for government benefits. The big push factors spurring families to leave places such as the Northern Triangle include violence, political persecution, natural disasters, and poverty; the big pull factors drawing them in include the availability of work and the possibility of family reunification. It makes sense. If you are a Honduran family fleeing horrific poverty and miserable crime, what is going to be more appealing to you: moving where your cousins live and have found work, where they can help you get an apartment and help you put your kids through school, or moving where there is the option of enrolling in a health program for indigent workers regardless of immigration status? (To be clear, the United States bars legal immigrants from enrolling in the major federal benefit programs for years, and bars undocumented immigrants from ever participating.)