The welfare state could not function without judgments about how well off its citizens are. For example, governments devise progressive income taxes, which are designed to capture more wealth from the well off and less from the impecunious. These policies presume an ability to take a manageable amount of information about an individual\u27s income or assets and make judgments about her welfare. In fact, people do this all the time, mostly without thinking about the methodological problems involved. The superficial casualness of our daily observations about welfare belies the state of the economic science of welfare measurement. Economists have attempted to measure welfare scientifically for more than a century, but after an early period of ...