1. Profit Maximization and Derived Demand A firm’s hiring of inputs is directly related to its desire to maximize profits –any firm’s profits can be expressed as the difference between total revenue and total costs, each of which can be regarded as functions of the inputs used  = TR(K,L) - TC(K,L)

2. Profit Maximization and Derived Demand First-order conditions for a maximum are –the firm should hire each input up to the point at which the extra revenue yielded from one more unit is equal to the extra cost

3. Marginal Revenue Product The marginal revenue product (MRP) from hiring an extra unit of any input is the extra revenue yielded by selling what that extra input produces MRP = MR  MP

4. Marginal Expense If the supply curve facing the firm for the inputs it hires are infinitely elastic at prevailing prices, the marginal expense of hiring a worker is simply this market wage If input supply is not infinitely elastic, a firm’s hiring decision may have an effect on input prices

5. Marginal Expense For now, we will assume that the firm is a price taker for the inputs it buys  TC/  K = r  TC/  L = w The first-order conditions for profit- maximization become MRP K = r MRP L = w

6. An Alternative Derivation Profit maximization requires that MR = MC so we have MR  MP K = MRP K = r MR  MP L = MRP L = w

7. Price Taking in the Output Market If a firm exhibits price-taking behavior in its output market, MR = P This means that at the profit-maximizing levels of each input P  MP K = r P  MP L = w –sometimes P multiplied by an input’s MP is called the value of marginal product

8. Comparative Statics of Input Demand We will focus on the comparative statics of the demand for labor –the analysis for capital would be symmetric For the most part, we will assume price- taking behavior for the firm in its output market

9. Single-Input Demand Suppose that the number of truffles harvested in a particular forest is Assuming that truffles sell for $50 per pound, total revenue for the owner is

10. Single-Input Demand Marginal revenue product is given by If truffle searchers’ wages are $500, the owner will determine the optimal amount of L to hire by

11. Competitive Determination of Income Shares If the firm is profit-maximizing, each input will be hired to the point where its MRP is equal to its price Thus,

12. Monopsony in the Labor Market In many situations, the supply curve for an input (L) is not perfectly elastic We will examine the polar case of monopsony, where the firm is the single buyer of the input in question –the firm faces the entire market supply curve –to increase its hiring of labor, the firm must pay a higher wage

13. Monopsony in the Labor Market The marginal expense of hiring an extra unit of labor (ME L ) exceeds the wage If the total cost of labor is wL, then In the competitive case,  w/  L = 0 and ME L = w If  w/  L > 0, ME L > w

14. Monopsony in the Labor Market Labor Wage S ME D L1L1 The firm will set ME L = MRP L to determine its profit-maximizing level of labor (L 1 ) w1w1 The wage is determined by the supply curve

15. Monopsony in the Labor Market Labor Wage S ME D L1L1 w1w1 Note that the quantity of labor demanded by this firm falls short of the level that would be hired in a competitive labor market (L*) L* w* The wage paid by the firm will also be lower than the competitive level (w*)

16. Monopsonistic Hiring Suppose that a coal mine’s workers can dig 2 tons per hour and coal sells for $10 per ton –this implies that MRP L = $20 per hour If the coal mine is the only hirer of miners in the local area, it faces a labor supply curve of the form L = 50w

17. Monopsonistic Hiring The firm’s wage bill is wL = L 2 /50 The marginal expense associated with hiring miners is ME L =  wL/  L = L/25 Setting ME L = MRP L, we find that the optimal quantity of labor is 500 and the optimal wage is $10

18. Monopoly in the Supply of Inputs Imperfect competition may also occur in input markets if suppliers are able to form a monopoly –labor unions in “closed shop” industries –production cartels for certain types of capital equipment –firms (or countries) that control unique supplies of natural resources

19. Monopoly in the Supply of Inputs If both the supply and demand sides of an input market are monopolized, the market outcome will be indeterminate –the actual outcome will depend on the bargaining skills of the parties

20. Monopoly in the Supply of Inputs Labor Wage S ME D MR L1L1 w1w1 The monopoly seller would prefer a wage of w 1 with L 1 workers hired L2L2 w2w2 The monopsony buyer would prefer a wage of w 2 with L 2 workers hired