Listen to article(2 minutes)The engine of the U.S. economy—consumer spending—is starting to sputter.Retail purchases have fallen in three of the past four months. Spending on services, including rent, haircuts and the bulk of bills, was flat in December, after adjusting for inflation, the worst monthly reading in nearly a year. Sales of existing homes in the U.S. fell last year to their lowest level since 2014 as mortgage rates rose. The auto industry posted its worst sales year in more than a decade.