Figure 2.

Indifference curves vary for different types of goods. (a) Example indifference curves for perfect complements (left and right shoes of the same style and size); wearing only one shoe is of no use for individuals with two feet. (b) Example indifference curves for perfect substitutes (blue pens and black pens when colour does not matter); these goods are traded at a constant exchange rate, regardless of the amounts of goods on offer. (c) Example of non-convex indifference curve. Combined consumption reduces the utility of olives and chocolate. Thus, for combinations to reach the same utility as separate consumption requires additional olives and chocolates. (d) Example indifference curve with positive slope. The more of a negatively valued good people have to endure, the more of a positively valued good they require as compensation.