The hope that better externalities could make people lastingly happier was discouraged by a study of lottery winners, who were happier for a few months after their windfall but soon fell back to their habitual level of grouchiness or cheerfulness. We adapt rapidly to windfall, job promotion, or marriage, so theorists argue, and we soon want to trade up to yet more goodies to raise our plummeting happiness. If we trade up successfully, we stay on the hedonic treadmill, but we will always need yet another shot.
