In his immigration speech Wednesday night, Donald Trump threatened to cut off aid to cities that offer “sanctuary” to illegal immigrants. New York, like a number of other American cities, makes a strict point of not asking people about their immigration status when they interact with police, librarians, social-service providers, or other city officials. This system, it is said, promotes public safety by encouraging illegal aliens to report crimes, and enhances the economic life of the city. Estimates vary as to how many New Yorkers are here in violation of federal immigration law, but the number is at least 500,000 and could be as high as 800,000. The city’s political establishment argues continually that these immigrants are an unalloyed benefit to New York. But leaving aside the sentimental rhetoric about hard work and family values, actual facts about the costs and benefits of illegal immigration are hard to come by—since no one is allowed to inquire about immigration status. In an era of Compstat 2.0 and Big Data, statistics on the crime rate among illegal aliens are nonexistent, for example. New York’s sanctuary policy makes it difficult to break out the costs of harboring hundreds of thousands of unauthorized residents.

Instead of data, we get wildly implausible statements. For instance, on a radio call-in show, Mayor de Blasio gave a stirring denunciation of Trump’s immigration speech and made a vigorous defense of the city’s undocumented population. But he did it without facts. Illegal immigrants are “integral to all of our communities,” the mayor said, claiming that “4.3 million jobs in New York City” (i.e., all private and public employment) are “directly connected to [its] vibrant immigrant population.” De Blasio praised a caller who employs illegal aliens at his supermarket, in knowing violation of federal employment law, saying, “you’re giving them a job and I thank you for that.”

In a similar vein, city council speaker Melissa Mark-Viverito commissioned her finance division to weigh the economic impact on New York City if unlawful residents departed. Citing the liberal Institute on Taxation and Economic Policy, the analysis concludes that illegal immigrants pay $793 million in state and city taxes. However, the source data reveal that approximately 90 percent of that sum consists of sales and excise taxes, along with a backed-out estimate of the portion of rent that represents property tax.

Tax revenue is tax revenue, and hundreds of millions of dollars of sales tax is nothing to sneer at. But the implication of the city council’s analysis is that this money is somehow a gift to the city, as though the half-million-plus illegal aliens in New York don’t use the streets, schools, jails, subways, libraries, sanitation, fire department, and parks that those taxes pay for. And folding all tax revenue together disguises the fact that reported income by illegal aliens is quite low—because they’re largely working either off the books or with a stolen Social Security number.

Local politicians get angry every September, when public schools are unexpectedly operating at 150 percent capacity. They demand to know why the School Construction Authority didn’t plan ahead for population surges that are impossible to predict based on current demographic data. Roomy Victorian mansions in Dyker Heights or Douglaston are suddenly discovered to house 30 people in illegally subdivided units, with substandard electrical connections, dozens of trash bags on garbage day, and no means of egress in case of fire. Leaders then fulminate about gentrification and luxury developments in Manhattan.

One effective metric for understanding the costs of illegal immigration is health care. Because Medicaid is funded partially by the federal government, it is limited to U.S. citizens or lawful permanent residents. But the city’s Health + Hospitals Corporation, which runs New York’s massive public health infrastructure, takes it as its mission to provide care to anyone who needs it, without regard for immigration status. This policy is a major reason why HHC is on constant verge of financial collapse. During the last fiscal year, HHC needed an emergency allocation of $337 million from the city just to keep its doors open, and the prognosis for the future is even worse. At an April press conference, Dr. Ram Raju, president of HHC, said that caring for illegals consumes about one-third of his $7.6 billion annual budget. Rounding down, that means that $2.5 billion—of which the city is picking up an increasingly large chunk every year, as state and federal aid dries up—goes toward providing health care to illegal aliens in New York.

In a city budget of $82.2 billion, that $2.5 billion represents a significant piece of the pie. Mayor de Blasio says that New Yorkers are happy to shoulder the cost of caring for their unlawfully resident neighbors, and maybe they are. But until we’re allowed to determine the real numbers and make a meaningful accounting of the costs and benefits, all we have to go on are sentiment and hollow rhetoric.

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