產(chǎn)業(yè)組織理論課件：Lecture 7 Test of SCP Model

1、產(chǎn)業(yè)組織理論Industrial organization Lecture 7 Test of SCP Model OutlineStatistical tool for evaluating SCP modelMeasurement issuesMeasurements of market structureTheoretical research on SCP modelsEarly studiesEconometric studiesConceptual studiesStatistical tool for evaluating SCP model實證工作在產(chǎn)業(yè)組織領(lǐng)域一直是一個非常重

2、要的部分。許多研究聚焦于分析市場結(jié)構(gòu)和非完全市場競爭中企業(yè)行為的實證方法上產(chǎn)業(yè)組織理論的實證研究成果主要應(yīng)用于反壟斷政策的實施、管理機(jī)構(gòu)的決策以及與政府或公司的合作中的實驗性研究設(shè)計這類研究的特點主要體現(xiàn)在靜態(tài)的橫截面和案例研究上，以及動態(tài)問題研究上Statistical tool for evaluating SCP model結(jié)構(gòu)-行為-績效研究產(chǎn)業(yè)組織理論的結(jié)構(gòu)學(xué)派代表人物梅森和貝恩及其早期追隨者研究的最重要的問題是：在不完全競爭的美國和世界市場上的是否存在經(jīng)濟(jì)無效率?梅森和貝恩認(rèn)為了解市場結(jié)構(gòu)可以預(yù)知市場行為和績效，從而為政策制定者提供依據(jù)。如果壟斷者或者寡頭壟斷者和在完全競爭市場上表

3、現(xiàn)的一樣，那么政府就沒有理由干涉市場的結(jié)構(gòu)和行為如果壟斷者或者寡頭壟斷者一直沒有完全競爭市場下的表現(xiàn)好，那么政府就有充分的理由干涉Statistical tool for evaluating SCP modelSCP模式研究的是市場結(jié)構(gòu)中的多種要素和績效之間的關(guān)聯(lián)，傳統(tǒng)的SCP研究方法認(rèn)為市場結(jié)構(gòu)的某些要素提高了共謀的可能性，這種共謀的行為導(dǎo)致了更高的價格和利潤SCP研究通過市場結(jié)構(gòu)的各種特征和績效之間關(guān)系的證據(jù)對市場勢力做出一些推斷，如果研究發(fā)現(xiàn)集中度越高利潤就越高，那么SCP的解釋是，在高集中度的行業(yè)中企業(yè)可以更好地共謀，這就導(dǎo)致了高價格、高利潤以及資源的非優(yōu)化配置Statistical

4、 tool for evaluating SCP model結(jié)構(gòu)學(xué)派的早期經(jīng)濟(jì)學(xué)家側(cè)重尋找結(jié)構(gòu)、行為和績效三者之間的經(jīng)驗聯(lián)系和統(tǒng)計數(shù)據(jù)上的關(guān)聯(lián)。這種分析并沒有以公開的共謀行為作為基礎(chǔ)，而是假設(shè)結(jié)構(gòu)、行為和績效之間存在某種關(guān)聯(lián)，那么行業(yè)的利潤和行業(yè)集中度的測量之間就存在聯(lián)系，它表現(xiàn)為一系列追求利潤最大化的行業(yè)行為這些行為導(dǎo)致了對價格和產(chǎn)量的選擇，這種選擇最終決決定了行業(yè)的利潤。經(jīng)濟(jì)學(xué)家的工作就是尋找市場結(jié)構(gòu)和價格或者利潤之間的經(jīng)驗關(guān)系。如果市場集中度與價格或者利潤正相關(guān)，那么就暗示了企業(yè)是在共謀而不管它們是不是真的在共謀Statistical tool for evaluating SCP mo

5、del研究市場結(jié)構(gòu)和經(jīng)濟(jì)績效之間關(guān)系的統(tǒng)計學(xué)工具主要是回歸分析 (regression analysis) 。這種量化經(jīng)濟(jì)關(guān)系的方法是通過經(jīng)濟(jì)數(shù)據(jù)來測試關(guān)于經(jīng)濟(jì)變量之間關(guān)系的假設(shè)。假設(shè)經(jīng)濟(jì)學(xué)家想要研究市場結(jié)構(gòu)和利潤之間的關(guān)系。完全競爭和壟斷理論中的一個隱含假設(shè)是:隨著市場集中程度不斷提高，經(jīng)濟(jì)利潤會不斷增加。用X代表市場集中度，Y代表經(jīng)濟(jì)利潤，則：該模型的建立以4類假設(shè)為基礎(chǔ)：經(jīng)濟(jì)學(xué)假設(shè)統(tǒng)計學(xué)假設(shè)計量經(jīng)濟(jì)學(xué)假設(shè)預(yù)測假設(shè)Statistical tool for evaluating SCP model散點圖可以用來初步確定兩個變量之間的關(guān)系。前提假設(shè)是市場的集中度越高經(jīng)濟(jì)利潤就越高，用X代表橫軸

6、，用Y代表縱軸如果關(guān)于市場集中度和經(jīng)濟(jì)利潤之間關(guān)系的假設(shè)是正確的，那么樣本數(shù)據(jù)的散點圖就應(yīng)該像圖(a)；如果這個假設(shè)不正確，那么散點圖就會像圖（b）那樣。如果利潤率與多種結(jié)構(gòu)因素有關(guān)，則可以用多元回歸方程：Statistical tool for evaluating SCP modelStatistical tool for evaluating SCP modelStatistical tool for evaluating SCP modelMeasurement issuesMeasures of Performance The measures of market structure

7、 present serious difficulties because of the problems associated with correctly defining marketsMarket power permits a firm to raise price above the competitive level. This suggests that a good way to measure market power might be to look directly at pricesUnfortunately, looking at prices makes sens

8、e only for a given product. To make comparisons across industries or firms that produce a variety of products, a common denominator is necessary. One possible common denominator is costsMeasurement issuesOne possible common denominator is costs. The Lerner Index（P-MC）/P theoretically appealing becau

9、se it directly measures the increase of price above marginal costUnfortunately, the Lerner Index is difficult to estimate because data are lacking on firms marginal costsFour different measures have been used as a proxy for the Lerner Index in SCP studies: excess return on sales, profit rate, price-

10、cost margin, Tobins qNot surprisingly, none of these measures is idealMeasurement issuesExcess return on sales:the ratio of economic profits to sales revenue; under certain assumptions, this measure can be shown to equal the Lerner Index. Despite its theoretical appeal,few studies have used the exce

11、ss profit rate on sales to measure performanceA difficulty arises in the calculation of economic profits, which can be broken down into sales revenue minus noncapital costs minus depreciation minus annual capital costsTheoretically, annual capital costs equal the total capital stock multiplied by th

12、e competitive cost per unit of capitalMeasurement issuesExcess return on sales:Accounting data, however, do not report the competitive rate of return on capital; to measure the excess profit rate of return, a researcher must make a judgment about what the appropriate competitive rate of return isOne

13、 study, for example, used 6 % as the competitive rate of return, arguing that this rate of return approximates the after-tax rate of return on equity over the long run in competitive industriesMeasurement issuesProfit rate:Many researchers have used accounting profits as a measure of relative perfor

14、manceThese data are readily available from standard sources and do not require a judgment about the competitive rate of returnFor purposes of comparison across firms, profits are divided by some base figure to yield aprofit rate. or a rate of return. Earning positive economic profits is equivalent t

15、o earning a rate of return that is greater than the competitive rate of returnMeasurement issuesProfit rate:Suppose that a firm earns a 9 % rate of return. If investment in a competitive industry yields a 6% rate of return, then 9% is an excess rate of return, and we can conclude that the firm is ea

16、rning positive economic profitsNot surprisingly, there are potential problems with this measure of profits; accounting data need to be used with careMeasurement issuesProblems with accounting profits led researchers to turn to another measure of performance: the price-cost marginThe main advantage o

17、f using the price-cost margin rather than profit rates arises from the level of aggregation at which data are reported. Because profit rates are calculated from firm-specific data,reported profits for any diversified firm reflect profits from several industriesHence, it is difficult to match profits

18、 with industry-specific measures of structure, such as the concentration ratio. In contrast, the price-cost margin is calculated from data available in the Census of ManufacturesMeasurement issuesCensus data are reported at the level of the individual plant, which is typically much less diversified

19、than are firms。 Therefore, using Census data makes the fit between the measure of performance and the measures of structure much betterUnfortunately, the same feature that makes census data attractive can also be seen as a drawback. Because each plant shares certain joint costs with other plants in

20、the firm, researchers cannot use accounting profits to calculate rates of returnInstead, they typically estimate a price-cost marginMeasurement issuesA final measure of profitability used by many economists is Tobins q, the ratio of market value of a firm to the replacement value of its assetsIn a p

21、erfectly competitive industry in long-run equilibrium, the value of q would be 1; the market value of the 61 would just equal what it would cost to rebuild it. If q is greater than 1, the market value of the firm is greater than its replacement costIn this case, other firms would want to enter the i

22、ndustry, anticipating that the market value of their investment will be greater than its costMeasurement issuesThus, in the absence of barriers to entry and exit, q will be driven to 1; it will persist above 1 if entry is barred.Tobins q has several advantages over rate of return measures. The numer

23、ator of market value, reflects expected future profits, whereas accounting data reflect only past profitsAlso, the market value of a firm depends partly on risk, so q incorporates an adjustment for risk. In addition, q is much less sensitive to errors in measuring its components than are profitsMeas

24、urement issuesUnfortunately, q is not without problems. Like rate of return measures, q reflects the operations of the entire firm, creating complications for diversified firmsAlso, because accounting data are used to calculate the replacement cost, some of the objections accounting rates of return

25、also apply to estimates of qThese problems involve the measurement of a firms capital assets. Accountants use of depreciation schedules that do not reflect true economic depreciation is a problem of the calculation of q, as it is for the calculation of accounting rates of returnMeasurement issuesAls

26、o, replacement costs should include the value of intangible assets resulting from expenditur on advertising and R&DIf a researcher ignores these intangible assets, the denominator will be too low, leading to an estimate of q that is greater than one even for competitive firmsIn fact, one study estim

27、ated average Tobins q over the period 1960 to 1976 for a sample of U.S.industries, finding a median value of q of 1.35. This could indicate that firms typically earn positive economic profits or that measurement errors biased q upward. Without more information, it is not possible to distinguish one

28、explanation from the otherMeasurements of market structureMeasures of concentrationA key variable in most SCP studies is a measure of market concentration. There are several possible measures of market concentrationIdeally, oligopoly theory would indicate which measure of concentration is appropriat

29、e. Several authors have, in fact, used oligopoly theory to argue for a particular measure of concentrationIn an early article, Stigler advocated the (HHI), arguing that it can be used to detect cheating on collusive agreementsMeasurements of market structureMeasures of concentrationCowling and Water

30、son also favored the HHI; they showed that if firms behave as classic oligopolists, the HHIis related to the weighted average of firms price-cost marginsUnder alternative behavioral assumptions, however,the concentration ratio is the appropriate measureThomas Saving modeled an industry consisting of

31、 a dominant group of firms and a competitive fringe. Using this model, profits of the industry and of the dominant firms increase with CRn, the share of sales produced by the n dominant firmsMeasurements of market structureMeasures of concentrationUnfortunately,therefore,theory does not give us an u

32、nambiguous choice of concentration ratioFurthermore, given that some of the hypotheses of interest involve the effect of concentration on behavior, it is problematic to assume a particular model of behavior ex ante.Until theory can provide better guidance, it is advisable to view results that are se

33、nsitive to the choice of specification or of sample selection with cautionMeasurements of market structureMany economists have used proxies for a barriers as independent variables in their regression equations. Commonly used measures of barriers to entry include the following:Economies of scale: the

34、 ratio of midpoint plant sales to total industrial salesCapital requirement: the estimated amount of capital required by a midpoint plantProduct differentiation: the advertising intensity, measured by the ratio of advertising expenditures to salesResearch intensity: the ratio of R&D expenditures to

35、sales Measurements of market structureResearchers have used a variety of additional explanatory variables in SCP studiesOne is some measure of recent sales growth. This variable is included to control for the effects of disequilibriumA second variable is the degree of unionization. This variable is

36、included to test the hypothesis that a union may be able to capture at least some of the excess profits generated by product market power by bargaining for higher wagesTheoretical research on SCP modelsEarly studies:The first SCP empirical work primarily involved detailed case studies of individual

37、industriesThese studies were extremely time-consuming and greatly limited by data constraintsBeginning with the work of Bain in the 1950s, economists employed interindustry, cross-section approach to examine the relationships among various measures of market structure, conduct, and performanceTheore

38、tical research on SCP modelsEarly studies:By todays standards, the empirical approach that Bain used to test his hypotheses is simple. He gathered data on manufacturing industries and organized these data into groups according to a structural characteristic of interest, with the main focus on market

39、 concentrationAfter grouping the data, Bain compared average profit rates across groups to see if they differed. Bains measure of profits for each industry was the average of the largest firms(up to four per industry) accounting rate of return on stockholders equityTheoretical research on SCP models

40、Early studies:Bain conducted two studies examining the relationship between profitability and market concentration Bain hypothesized that firms in highly concentrated industries were better able to collude, which led to increased prices and profitsBain used data for 42 manufacturing industries and d

41、ivided his sample into two groups: those with an eight-firm concentration ratio above 70 percent and those with an eight-firm concentration ratio below 70 percent. As expected, Bain found that the more concentrated industries had higher average profit ratesTheoretical research on SCP modelsEarly stu

42、dies:In his second study. Bain examined the simultaneous effect of market concentration and barriers to entry on profitability. He predicted that profits would be higher in concentrated industries with high barriers to entry than in concentrated industries with low barriers to entryBain used a sampl

43、e of 20 manufacturing industries, noting that the amount of work needed to collecting formation about each industry imposed a practical limitation on the sample size. His sample covered the periods 1936-1940 and 1947-1951Theoretical research on SCP modelsEarly studies:Using Bains methodology, Mann g

44、ot similar results for data from 1950 to I960. In Manns sample, profits were higher in more concentrated industriesThe average rate of return for sample industries with eight-firm concentration ratios above 70% was 13.3%, whereas for industries in the less concentrated group, the average rate of ret

45、urn was only 9%Like Bain, Mann found a distinct difference between the average profit rates for the very high entry barrier group and the other two entry barrier groups Theoretical research on SCP modelsEconometric studies:Study by Collins and Preston. Their basic hypothesis was the same as Bains: m

46、ore highly concentrated industries should exhibit higher average profitsCollins and Preston regressed the price-cost margin (PCM) on the four-firm concentration ratio (CR4), the capital-sales ratio (CSR). and a measure of geographic dispersion (DISP)Their sample consisted of data for 417 industries

47、from the 1963 Census of Manufactures Theoretical research on SCP modelsEconometric studies:Collins and Preston estimated the following relationship:All three estimated coefficients have the expected sign and all are statistically significantThe main coefficient of interest for testing the hypothesis

48、 that higher concentration facilitates collusion and thus higher profits is that of the four-firm concentration ratio. statistically significant positive coefficient supports this hypothesisTheoretical research on SCP modelsEconometric studies:Study by Weiss: N = 399, R2 = 0.427PCM = 16.3 + 0.05CR4

49、- 0.029DISP + 0.119 CAP/S (2.08) (2.00) (7.44) + 1.3A/S - 1.9CAO + 0.023 INV/S + 0.26 GROW (7.20) (0.42) (0.169) (2.90) + 0.00083 CONS CR4 + 0.095 MID - 0.033 PLANTCAP (2.70) (0.38) (1.65) Theoretical research on SCP modelsDISP: an index of goegraphic dispersion CAP/S: the ratio of capitalto salesA/

50、S: the ratio of advertising to salesCAO: the ratio of central office employment to total employmentINV/S: the ratio of inventories to salesGROW = past output growthCONS CR4 : the four-firm concentration ratio multiplied by the percentage of industry sales going to consumer goods marketsMID: the rati

51、o of midpoint plant sales PLANTCAP: the estimated amount of capital required by a midpoint plantTheoretical research on SCP modelsWeisss results are consistent with the many cross-section industry-level studies of the determinants of profitability done in the 1960s and 1970s Such studies usually fou

52、nd the estimated coefficient of concentration to be positive and statistically significantGiven the general robustness of the results of cross-section industry studies done in the 1960s and 1970s, most economists accepted the SCP hypothesis underlying these regressionsHigher levels of concentration

53、were thought to facilitate collusion among firms, resulting in prices above marginal cost. This relationship appeared to be particularly strong in the presence of high barriers to entryTheoretical research on SCP modelsF ven as many additionalindustry-level studies throughout the 1970s confirmed the

54、 general structure-performance results, criticisms were raisedSkeptics pointed out a number of conceptual problems and problems of interpretation with the studiesCollusion versus efficiencyLarge versus small firmAssumption of linearityVariations over timeEndogeneity problemTheoretical research on SC

55、P modelsCollusion versus efficiencyOne important criticism concerns the interpretation of the observed statistical relationship between market concentration and profitabilityEconomists associated with the Chicago School, especially Harold Demsetz, noted that, rather than arising from collusion among

56、 leading firms, the statistical relationship between market concentration and profitability might be the result of efficiency.Theoretical research on SCP modelsCollusion versus efficiencyFurthermore, hundreds of studies have examined the robustness of the industry-level structure-performance results

57、 using different econometric techniques, samples, and explanatory variables.Some studies examined the effects of competition from foreign suppliers. As theory suggests, imports as a percent of domestic sales are negatively associated with profitabilityThe ability of domestic firms to exercise market

58、 power is limited by competition from foreign firmsTheoretical research on SCP modelsWhat is the connection between the supposed true relationship between market share and profits at the firm level and the observed relationship between concentration and profit at the industry level? The link is that

59、:High market shares lead to high levels of industry concentrationProfits of large firms receive more weight than profits of smaller firms in the calculation of the industry average level of profitsTherefore, more highly concentrated industry would, in fact, be associated with higher average profit l

60、evelsTheoretical research on SCP modelsOne way to discriminate between the collusion hypothesis and the efficiency hypothesis is to include both concentration and market share in the same equationStudy by Ravenscraft are:PCM=-22.3 + 0.183S 0.022CR4 + Other variables(4.95)(1.38)N= 3.186, R2 = 0.208(t