In: Economics
Suppose the demand and supply curves of a perfectly competitive market are:
Supply: Q = P - 10
Demand: Q = 90 - P
(1) Solve for the market equilibrium (price and quantity at
equilibrium)
(2) Solve for Welfare (Total Surplus).
(3) Suppose a per-unit tax of $10 is imposed in the market.
Calculate tax revenue and deadweight loss.
1) Market equilibrium has Qs = Qd
P - 10 = 90 - P
2P = 100
P = $50 per unit (market price)
Q = 90 - 50 = 40 units (market quantity)
2) Total surplus = CS + PS
= 0.5*(90 - 50)*40 + 0.5*(50 - 10)*40
= $800 + $800
= $1600
3) New demand is Q = 90 - (P + 10) or Q = 80 - P. New market outcome has
80 - P = P - 10
90 = 2P
P = 45 (sellers)
P = 55 (buyers)
Q = 45 - 10 = 35 units
DWL = 0.5*tax*reduction in quantity = 0.5*10*5 = $25
Revenue = tax*quantity = 10*35 = $350