Looking back on the first year of his second term, President Donald Trump boasts that he has resurrected the American economy by imposing big import taxes on foreign products. He made his case in a recent opinion piece in The Wall Street Journal, chiding the paper and critics, including mainstream economists, who predicted that tariffs would backfire, raising prices and threatening growth. "Instead,'' he wrote, "they have created an American economic miracle."

But the proof he offers is often off-base or wrong altogether.