206 ❖ Chapter 11/Public Goods and Common Resources
c. The total cost would be $8 3 = $24. If the cost were divided evenly among the
roommates, each would pay $6. Judd values three movies at $18 so his surplus would be
$12. Joel values three movies at $12 so his surplus would be $6. Gus values three
movies at $6, so his surplus would be $0. Tim values three movies at $3 so his surplus is
-$3. Total surplus among the three roommates would be $15.
d. The costs could be divided up by the roommates based on the benefits they receive.
Because Judd values the movies the most, he would pay the greatest share. The problem
6. a. Because knowledge is a public good, the benefits of basic scientific research are available
to many people. The private firm doesn’t take this into account when choosing how
much research to undertake; it only takes into account what it will earn.
7. When a person litters along a highway, others bear the negative externality, so the private
costs are low. Littering in your own yard (or perhaps your neighbors’ yards) imposes costs on
you, so it has a higher private cost and is thus rare.
8. a. The productivity of each fisherman declines as
N
rises because the fish in the town lake
are a common resource. It is not excludable but rival in consumption. The fish on the
farm is a private good because it is excludable and rival in consumption.