When Donald J. Trump’s professors at the Wharton School were teaching about the evils of tariffs, he probably acted like the delinquents in Ferris Bueller’s Day Off, staring sullenly as Ben Stein droned on about Smoot and Hawley and the Great Depression – or, like Ferris himself, was simply taking the day off.  Now we’re all paying a stiff price for Mr. Trump’s ignorance of history and economics.
 

The President has pitched his trade war against Canada, Mexico, and China as "bringing wealth back to America."  But when he stopped merely threatening and actually imposed his tariffs, the S&P 500 Index fell 8% and the NASDAQ 10%.  Overall, U.S. stocks have lost over $4 trillion in value (and rising, as this is written).  At his inauguration, Mr. Trump promised an economic “boom like no other.”  He is delivering an epic bust, and now speaks of a “period of transition.”
 

If you think this is just a problem for “the elites,” think again.  About 62% of Americans own stocks.  Even if you do not, however, this “transition” will hurt.  Investors are forward-looking:  falling stock prices reflect their judgment that these new taxes on imports will raise prices to consumers and reduce net revenue to businesses.  That will lead to declining output, layoffs, and reduced incomes.  Whether we call that a recession or not will depend on the severity and length of the pain, but there will be pain.
 

But won’t protecting domestic industries from foreign competition “bring jobs home?”  Fuel prosperity?  That’s what Tariff True Believers (and Mr. Trump’s inner circle, unfortunately, contains a few) always claim – erroneously.  Even if our trading partners do not retaliate with (unwise) tariffs of their own, the dollars we no longer send abroad for, say, Canadian lumber or Mexican produce can’t come back to us to buy American appliances or chemicals.
 

Protecting certain domestic industries, in other words, invariably damages others – except they don’t know who they are yet and, so, don’t lobby against the tariffs.  Therein lies the political momentum to do a foolish, self-destructive thing.  A recent Brookings Institution study estimates the Trump tariffs will reduce our exports by 6% (or 9% with retaliatory tariffs), destroy 177,000 jobs (or 400,000 with retaliation), and raise inflation by 1.33 percentage points (or 0.77 with retaliation).
 

People who pay attention to history know all this.  Tariffs invariably backfire; like taxes generally, they are anti-growth.  The most notable example of tariffs’ potential for catastrophic effects, of course, is the one with which Mr. Stein (the son of a great economist) bored Ferris Bueller’s classmates:  as the U.S. economy slowed in 1929 (thanks to the Fed’s contractionary monetary policy) we blamed foreigners for our pain, so Senator Reed Smoot and Representative Willis C. Hawley wrote a bill to punish them.  Over 1,000 economists signed a petition asking President Herbert Hoover to veto it, but he signed the Smoot-Hawley tariffs into law on June 17, 1930.
 

The rest, as they say, is history.  And you know what they also say about those who ignore history.
 

Stephen J.K. Walters (swalters@mdpolicy.org) is the author of Boom Towns:  Restoring the Urban American Dream, and Chief Economist at the Maryland Public Policy Institute.