Richard H. Thaler
Traditional economics assumes people are hyper-rational robots, but Richard Thaler proves we are predictably irrational humans who often misbehave.
The "endowment effect" causes people to value items they already own much more highly than identical items they do not possess.
"Loss aversion" suggests that the pain of losing something is psychologically twice as powerful as the pleasure of gaining it.
Through "mental accounting," individuals irrationally treat money differently depending on where it came from or what it is saved for.