The idea of a four-day workweek is catching attention. Young workers in particular see it as the wave of the future, while others worry it will undermine America prosperity. Economists have pondered the viability of a four-day workweek since research by Janice Hedges in 1971. Recently, though, a magical idea has come to the fore: Let employees work one fewer day per week at the same hours per day and same pay, and they will accomplish just as much as in a standard five-day workweek. All the fuss prompted us to ask several hundred American business executives and several thousand...