"There are systemic and systematic ways in which people do not behave according to what is traditionally called rationality. If given a choice between red lettuce and green lettuce, do you make the same decisions? Do you change your decision as prices change? That kind of framework doesn't work so well when you're making choices about savings rate or decisions about [the] portfolio for your retirement. At the end of your life you can say, "I wish I saved more" or "I wish I saved less." But you can't learn from that experience unless you believe in reincarnation. That's it. And your children can't learn very much because they are going to live in a very different world. So the models of rational behavior that were derived from choices between red lettuce and green lettuce don't apply to these lifetime decisions. We have to understand better how people make those kinds of decisions. Part of that is the role of those around them, what you might call the sociology of economics." -- Joseph Stiglitz, 3/25/2010