Demand and Supply
ANSWER TO TRY IT! PROBLEM
DVD rental store clerks are a factor of production in the DVD rental market. An increase in their wages raises the cost of production, thereby causing the supply curve of DVD rentals to shift to the left [Panel (a)]. (Caution: It is possible that you thought of the wage increase as an increase in income, a demand shifter, that would lead to an increase in demand, but this would be incorrect. The question refers only to wages of DVD rental store clerks. They may rent some DVD, but their impact on total demand would be negligible. Besides, we have no information on what has happened overall to incomes of people who rent DVDs. We do know, however, that the cost of a factor of production, which is a supply shifter, increased).
An increase in the price of DVD rentals does not shift the supply curve at all; rather, it corresponds to a movement upward to the right along the supply curve. At a higher price of P2 instead of P1, a greater quantity of DVD rentals, say Q2 instead of Q1, will be supplied [Panel (b)].
An increase in the number of stores renting DVDs will cause the supply curve to shift to the right [Panel (c)].