Anti-immigration advocates have long argued that tightening our borders is about protecting American jobs. Liberal immigration policies, they say, flood the market with cheap labor, suppressing wages and employment.

But a paper in the June issue of the American Economic Review finds that one of the largest attempts to help American workers by establishing immigration barriers did not accomplish its goals.

Authors Michael Clemens, Ethan Lewis, and Hannah Postel examined what happened when roughly half a million Mexican farm workers were blocked from entering the United States. The 1960s era policy change was intended to improve wages and employment for US farm workers by restricting the labor supply.

The policy targeted Mexican bracero workers, low-skilled farm laborers who were allowed to work in the US on seasonal contracts after World War II. The Kennedy administration began curtailing the number of braceros in 1962 and president Johnson eventually ended the program two years later. The policy shift was aimed at improving jobs for American farm hands. It did not have the intended effect.

Figure 2 from Clemens et al. (2018)

The figure above shows the Mexican fraction of hired seasonal farm labor in three groups of states: those with high exposure to Mexican workers (such as California and Texas), those with low exposure (Colorado, Minnesota, Oregon, etc.), and those with no exposure (Connecticut, Maryland, Pennsylvania).

True enough, the fraction of Mexican workers in high exposure states plummeted in 1965 (panel A) when they were no longer able to come to the United States. But there was virtually no impact on wages. Hourly wage increases in high exposure states followed roughly the same trajectory as in no exposure states and, if anything, appear to have risen more slowly by comparison.