Over the past few years, I have fielded versions of the same question from readers again and again: Who, exactly, is buying all of this stuff?The confusion is fair. Recent economic headlines do not add up to a coherent picture: Since 2020, Americans have spent lavishly on discretionary goods and services, even as the cost of necessities has soared. Consumer debt has ballooned right along with prices, and Americans are now defaulting on their credit cards at rates unseen since the Great Recession...