The idea that the happiness of people should be a goal of public policy is not new. As early as 1809, Thomas Jefferson stated publicly his belief that “the care of human life and happiness… is the only legitimate object of good government.” And yet, for the lion’s share of human history, we have gauged societal wellbeing according to much cruder metrics, like national income. Of course, what makes people richer and what enables their flourishing are not always...