Immigrants are to blame for unemployment, assert the class warriors at Salon.com. Philip Cafaro, a philosophy professor at Colorado State University and author of How Many Is Too Many?: The Progressive Argument for Reducing Immigration into the United States, claims in a recent post that immigrants are to blame for the relatively higher unemployment rate in construction and other lesser-skilled industries. But his argument is undone by history.

Cafaro’s post is full of inaccuracies, but a central point is that the higher the immigrant share of an industry, the greater the unemployment. Citing a Center for Immigration Studies analysis by Steven Camarota, he states, “Crucially, immigration-driven competition has been strongest among poor and working-class Americans … high percentages of immigrant workers within an economic sector strongly correlates with high levels of unemployment.”

Cafaro’s argument is flawed because it only takes a snapshot of unemployment in a given year (2004) when immigrants happen to have a higher share of the labor force. But if we go back to the 1950s and 1960s when the immigrant population was declining, we can see that the construction unemployment rate is always higher than the national rate.

From 1950 to 1970, the national unemployment rate averaged 4.7 percent. Construction unemployment was more than double at 10.4 percent. The immigrant share of the labor force during this period declined from 8.1 percent and 5.2 percent. In 2013, although immigrants accounted for 16 percent of the overall labor force and about a quarter of the construction industry, the industry’s unemployment rate (8.9%) was still over the national rate (6.2%).

In other words, regardless of the number of immigrants, the construction industry has a higher unemployment rate. In fact, in the more recent period from 2005 to 2014, the industry’s unemployment rate averaged only 40 percent above the national rate compared to 64 percent higher in the 1950 to 1970 period.

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Higher construction unemployment is mainly a product of the temporary and seasonal nature of construction jobs. Construction tasks are inherently time-stamped for completion and are often undoable during certain times of the year. The average monthly unemployment numbers for the industry bears this out. As the graph below shows, the number of construction jobs surged in 2014 to the point that the construction unemployment rate was actually lower than the national rate during the summer months.

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Immigrants are not the cause of higher construction unemployment. In fact, despite the higher annual levels of unemployment, local shortages in the industry occur periodically throughout the year, as I discussed in this prior post. Immigrants are important contributors to construction growth, and America’s closed-door policy toward migrant workers hurts the industry and the American economy.