The inclination of individuals to improve their performance when it lags behind that of others with whom they naturally compare themselves can be harnessed to optimize the individuals’ effort in work and study. In a given set of individuals, we characterize each individual by his relative...

The Gini coefficient features prominently in Amartya Sen’s 1973 and 1997 seminal work on income inequality and social welfare. We construct the Gini coefficient from social-psychological building blocks, reformulating it as a ratio between a measure of social stress and aggregate income. We...