Because people face trade-off making decisions requires compering the costs and benefits of alternative courses of action. In many cases, however, the cost of some action is not obvious as it might first appear. Consider, for example, the decision to go to college. The benefit is intellectual enrichment and a lifetime of better job opportunities. But what is the cost? To answer this question, you might be tempted add up the money you spend on tuition, books, room, and board. Yet this total does not truly represent what you give up to spend a year in college. The first problem with this answer is that it includes some things that are not really costs of going to college. Even if you quit school, you need a place to sleep and food to eat. Room and board are costs of going to college only to the extent that they are more expensive at college than elsewhere. Indeed, the cost of room and board at your school might be less than the rent and...