suppose, in the clam fishing example introduced in 7-2, a tax is applied per pound of calms harvested, rather than per fisher day. This tax, in other words, works to lower revenues rather than raise costs. At what level should the tax be set to bring about the socially efficient use level?

Table 7-2 Daily Costs and Returns from Clam Fishery Catch per fisher (pounds Cost per Net returns Aggregate net returns per fisher Number of fishers 1 2 3 4 5 6 7 8 9 10 per day) 20 20 20 20 18 16 14 12 10 8 Total catch revenue)* 20 40 60 80 90 96 98 96 90 80 fisher $12 12 12 12 12 12 12 12 Total costs $12 24 36 48 60 72 84 96 108 120 8 8 8 8 6 4 2 $8 16 24 32 30 24 14 0 -18 -40 12 12 *On the assumption that each unit of shellfish has a market value of $1. Table 7-2 Daily Costs and Returns from Clam Fishery Catch per fisher (pounds Cost per Net returns Aggregate net returns per fisher Number of fishers 1 2 3 4 5 6 7 8 9 10 per day) 20 20 20 20 18 16 14 12 10 8 Total catch revenue)* 20 40 60 80 90 96 98 96 90 80 fisher $12 12 12 12 12 12 12 12 Total costs $12 24 36 48 60 72 84 96 108 120 8 8 8 8 6 4 2 $8 16 24 32 30 24 14 0 -18 -40 12 12 *On the assumption that each unit of shellfish has a market value of $1