Perfect Complements Suppose now that someone offered you bundles of shoes.
Some of the shoes fit your left foot, others your right foot. How would you rank
these different bundles?
In this case, you might care only about the number of pairs of shoes. In other
words, you would judge a bundle based on the number of pairs you could assem-
ble from it. A bundle of 5 left shoes and 7 right shoes yields only 5 pairs. Getting 1
more right shoe has no value if there is no left shoe to go with it.
We can represent your preferences for right and left shoes with the indifference
curves in panel (b) of Figure 5. In this case, a bundle with 5 left shoes and 5 right
shoes is just as good as a bundle with 5 left shoes and 7 right shoes. It is also just
as good as a bundle with 7 left shoes and 5 right shoes. The indifference curves,
therefore, are right angles. In this extreme case of right-angle indifference curves,
we say that the two goods are perfect complements.
In the real world, of course, most goods are neither perfect substitutes (like
nickels and dimes) nor perfect complements (like right shoes and left shoes).
More typically, the indifference curves are bowed inward, but not so bowed that
they become right angles.
perfect substitutes two goods with straight- line indifference curves FIGURE 5 When two goods are easily substitutable, such as nickels and dimes, the indifference curves
are straight lines, as shown in panel (a). When two goods are strongly complementary, such
as left shoes and right shoes, the indifference curves are right angles, as shown in panel (b).
Perfect Substitutes and Perfect Complements Dimes 1
2
3
7
5
0
Nickels 6
4
2
(a) Perfect Substitutes
