Donald Trump won the presidency–despite losing the popular vote by 2.8 million—with a campaign that careened wildly from one distraction to another. He has clung to this as a Twitter and governing strategy ever since. As there are 190 countries in the world, and the United States trades with most of them, trade wars so far have provided a shovel-ready supply of such diversions. So, here we are: Last Thursday, just in time to distract from the more potentially violent foreign ventures that are not going very well (Iran, Venezuela), Trump announced plans for a new set of tariffs against Mexico.

This trade war is different from other trade wars: It’s not about trade. It’s not even about “trade” in the expanded, grossly misleading but commonly used definition that includes the intellectual property and investors’ “rights” that Trump is fighting for against China. It’s just Trump telling Mexico that they must stop the flow of migrants across our southern border or he will impose a 5 percent tariff beginning June 10 and increasing to 25 percent by October.

Unsurprisingly, this strategy has met with an unusual level of resistance from Republicans in Congress, as well as from other allies with deep pockets and money to lose if the war escalates, such as the U.S. Chamber of Commerce and Business Roundtable. Late Tuesday, after the president told Republicans that they would be “foolish” to try to stop him, The New York Times reported that Republican senators have warned the White House they could “muster an overwhelming majority to beat back the tariffs.” So it’s not clear yet whether this plan will actually take effect.

Still, it’s worth looking at the underlying reality of the “border crisis” that Trump has labelled a “national emergency” and which the tariffs purport to address—as well as how tariffs would actually affect that reality.

The most up-to-date measure that we have of migrants crossing the border between the U.S. and Mexico without authorization is the Custom and Border Protection’s “apprehensions/inadmissibles.” Over the past five years (fiscal years 2014 to 2018) this number has actually fallen, with 2017 apprehensions hitting nearly half-century lows. In 2018, apprehensions/inadmissibles went up, but were still well below the level of 2014. The number of unauthorized Southwestern border crossings, meanwhile, for any of these years (between 416,000 and 569,000) is just a fraction of the 1.6 million that crossed the border from Mexico in 2000.