Why indifference curves usually not be upward sloping?

Answer 1

Indifference curves are typically not upward sloping because they represent tradeoff's between economic "goods," things we like to have. For example, you might be willing to trade two scoops of vanilla ice cream for one slice of apple pie. You would be happier if you had both, but that would put you on a higher indifference curve. You are indifferent between two scoops of vanilla ice cream and once slice of apple pie-you value them equally. This can change as we move along indifference curves, because the "marginal utility" you get from consuming a given good begins to diminish after awhile (if you've already had eight scoops of ice cream, another probably doesn't look so good right now). If you only had one slice of apple pie, you would not trade it for one scoop of ice cream, but perhaps if you had three pieces of pie you would. If you had sixty pieces of pie, you almost certainly would.

Sometimes we do see indifference curves slope upward. We could frame that as work hours and income perhaps (the model really only works for people who can choose the number of hours they spend working). Say I dislike my job, but I like money. And that I make $10 an hour. I might be willing to work six hours in exchange for $60, but to get me to work 8 hours, you'll have to pay me $80. This indifference curve slopes upward, because the exchange is between an economic good, and an economic "bad."