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1、Steven Landsburg, University of RochesterChapter 6Production and CostsCopyright 2005 by Thomson South-Western, part of the Thomson Corporation. All rights reserved.Introduction 生產函數決定成本函數，而(邊際)成本會影響供給函數；因此，本章先介紹生產函數，然後說明成本函數。 生產函數在說明生產要素與產量之間的關係；生產要素分為兩類，一類是短期即可變動其使用的數量的(以勞工為代表)，另一類是長期才可變動其使用的數量的(以資
2、本為代表) 。 產量受到生產技術與生產要素的影響 Where do cost curves come from Depends on firms available technology Determines production process Production process determines firms costs2Production and Costs in the Short Run Limited options in short run (SR) Initial assumption Firm can hire more labor3Production in the
3、Short Run Total product (TP) of labor Quantity of output produced by firm in a given amount of time dependent on labor hired Information graphically represented by production function Production function slopes upward Production function is rule for determining how much output can be produced with a
4、 given basket of inputs4Calculating MP and AP Marginal product of labor (MPL) Increase in total product based on hiring one additional worker Assume capital fixed Slope of TP Average product of labor (APL) Total product divided by number of workers5Relation between MP and APNTP6Calculating MP and AP
5、MPL&APL8EXHIBIT 6.1Total, Marginal and Average Products9Shape of MP and AP Curves AP If number of workers large, additional workers cause average product of labor to decrease Inverted U-shape MP Inverted U-shape AP and MP relationship to one another If MP AP, MP lies above AP If MP AP, MP lies below
6、 AP If MP = AP, AP at maximum or peak10EXHIBIT 6.2The Stages of Production11Variable Costs in the SR Constructing the firms variable cost curve Need total product curve Need wage rate Price of hiring labor Multiply number of workers by wage rate to get variable cost PLL=VC Curve relates total produc
7、t, not number of workers, to variable cost12Exhibit 6.3 VC CurveNTPQVCTC15515652121230803212145954282860110533337512563636901407373710515513EXHIBIT 6.3Variable Cost Curve14Fixed Costs in the SR Costs of capital Physical assets, such as machinery and factories Ex. handymans van15Total Cost Total cost
8、 equal to sum of fixed and variable costs of productionTC=FC+VC=FC+PLL Additional cost considerations beside totals16Computing Average and Marginal Costs Average variable cost (AVC): variable cost divided by quantity of output Labor only variable factor of production Calculate AVC by taking the wage
9、 rate and dividing by APL Average cost (AC): total cost divided by quantity of output Sometimes called average total cost Marginal cost (MC): additional cost attributable to the last unit of output produced Labor only variable factor of production Calculate MC by taking the wage rate and dividing by
10、 MPL17Computing Average and Marginal Costs18EXHIBIT 6.4Deriving the Average and Marginal Cost Curves19MC&AC20Shapes of Cost Curves VC curve always increasing More output requires more labor Higher costs TC curve determined by sum of FC and VC FC constant Has same shape as VC curve MC, AC, and AVC cu
11、rves are U-shaped21EXHIBIT 6.5The Geometry of Product Curves and Cost Curves22Cost Curves Relations MC relationship to AVC and AC MC below AVC, AVC falling MC above AVC, AVC rising MC equals AVC, AVC at minimum Can replace AVC with AC, same holds true Shapes of cost curves related to shapes of produ
12、ct curves23Production and Costs in the Long Run In long run (LR), firm can adjust employment of capital and labor Attempts to achieve the least cost method of producing a given quantity of output24Isoquants Geometry of LR production Label vertical axis with K, stands for capital Label horizontal axi
13、s with L, which stands for labor Fixed period of time Want to use least costly method Avoid technologically inefficient points which are outside the boundary General observations Slope downward Fill the plane Never cross Convex25Marginal Rate of Technical Substitution Absolute value of slope of isoq
14、uant MPL divided by MPK Amount of capital necessary to replace one unit of labor while maintaining a constant level of output If much labor and little capital employed to produce a unit of output, MRTSLK is small Geometrically isoquant is convex26EXHIBIT 6.8The Production Function27Choosing a Produc
15、tion Process Minimizing cost important part of maximizing profit Isocost allow to keep track of costs Set of all baskets of inputs that can be employed at a given cost Slope: -PL/PK Minimizing cost and maximizing output requires firm choose tangency point between an isocost and an isoquant Means tha
16、t MRTS = PL/PK Tangencies lie along curve called the firms expansion path28EXHIBIT 6.9Cost Minimization29Long-Run Cost Curves Information needed Production function or isoquants Input prices Firms long-run total cost Cost of producing a given amount of output when the firm is able to operate on its expansion path Long-run average cost Long-run total cost divided by quantity Long-run marginal cost Part of long-run total cost attributable to the last unit produced30EXHIBIT 6.11 Deriving Long-Run T
