Theoretical Economics Letters
Vol.05 No.04(2015), Article ID:58576,8 pages
10.4236/tel.2015.54058
Exploitation in Monopsony
Chung-Cheng Lin
Institute of Economics, Academia Sinica, Taipei, Taiwan
Email: cclin@econ.sinica.edu.tw
Copyright © 2015 by author and Scientific Research Publishing Inc.
This work is licensed under the Creative Commons Attribution-NonCommercial International License (CC BY-NC).
http://creativecommons.org/licenses/by-nc/4.0/


Received 16 June 2015; accepted 2 August 2015; published 5 August 2015
ABSTRACT
A key feature of monopsony model is that a single firm pays its workers a wage (w) less than the marginal revenue product (MRP). This feature has been explained as a synonym of the single firm exploiting its workers since its creation by Joan Robinson [1] . By using a simple standard efficiency wage model of Yellen [2] , this paper examines the conventional wisdom by showing that the firm pays workers
in the equilibrium of full employment, but paradoxically pays them
in the equilibrium of involuntary unemployment. According to the conventional wisdom that the result of
implies that workers are exploited by the firm, this finding indicates that the firm does not exploit its employees (
) when there are involuntary unemployed workers queuing for jobs, but paradoxically exploits workers (
) when there are no workers queuing for jobs. The finding is obviously counter-intuitive. This counter-intuitive finding reveals that the key feature of
in monopsony cannot be regarded as a proper theoretical basis for the issue of labor exploitation.
Keywords:
Monopsony, Exploitation, Efficiency Wages

1. Introduction
The origin of the theoretical analysis of monopsony can be traced back to the Joan Robinson [1] classical work―The Economics of Imperfect Competition. Monopsony originally refers to a market structure in which there is only a single buyer. In a survey paper, Boal and Ransom [3] consider that the term “monopsony” nowadays can be applied more broadly to any model where each individual firm faces an upward-sloping labor supply curve and has the market power to set the wage, no matter how many buyers there are in the labor market1. Similarly, in a book, Manning [4] extends the scope of monopsony to include models where there are important frictions in the labor market and employers set wages. Manning [4] claims that “the main advantage of the monopsonistic approach is that the way one thinks about labor markets is more ‘natural’ and less forced”. Manning [4] advocates “the belief that a perspective on labor markets based on the view that ‘monopsony’ is important led to a much better understanding of a very wide range of labor market phenomena”2.
The main feature of monopsony is that the firm pays its employees a wage (w) that is less than the marginal revenue product (
). Joan Robinson [1] interprets this result as a case where the employer exploits employees3, and indicates that the reason for the exploitation “is due to imperfection of the labour market” (p. 299)4. Arthur Pigou [10] uses the value
to measure the degree of exploitation. Many other authors, following Robinson and Pigou, have examined to what extent workers are exploited by a single employer or a few employers. Most of the research interest focuses on whether or not the multi-million-dollars-a-year professional athletes are exploited5, and the empirical findings indicate that they are always underpaid6. Recently, monopsony has been used to explain a variety of facts that are difficult to explain in the competitive labor model, such as the positive employment effect of minimum wages, the provision of general training, wage dispersion, and employment size-wage effect7.
This paper examines the exploitation explanation in a standard efficiency wage model of Yellen [2] 8. In this simple efficiency wage model, there is a single firm having the market power to set the wage (the same assumptions as in the Robinson monopsony model), and the labor market equilibrium may be characterized by either full employment or involuntary unemployment (the full-employment Robinson model is an extreme case of this model). This study shows that when the labor market equilibrium results in full employment, workers are paid less than the marginal revenue product (
). The result is the same as that of the (full-employment) Robinson model, the so-called exploitation occurs. By contrast, when the labor market is in the equilibrium of involuntary unemployment, workers are paid according to their marginal revenue product (
). In this non-full-employment case, even though there is only a single buyer, the so-called exploitation does not occur.
According to the conventional wisdom that the result of
implies workers are exploited by the firm, we find that the firm does not exploit its employees when there are involuntary unemployed workers queuing for jobs, but paradoxically exploits them when there are no workers queuing for jobs. Since the wage bargaining power of workers is weaker in the case of involuntary employment than in the equilibrium of full employment, the finding is obviously confusing and counter-intuitive. This paradoxical result motivates this paper to reexamine the validity of exploitation explanation and leads to the conclusion that the key feature of
in monopsony cannot be considered to be a solid theoretical basis for the issue of labor exploitation.
The rest of this paper proceeds as follows. Section 2 presents and analyzes a standard efficiency wage model. Section 3 discusses the validity of exploitation viewpoint in monopsony. A final comment is presented in Section 4.
2. The Model
The basic tenet of the efficiency wage theory is that the effort (productivity) of a typical worker is positively related to his/her wage, and firms have the market power to set the wage9. Since a lower wage implies lower productivity, it may be profitable for firms not to lower their wages in the presence of involuntary unemployment. The theory is generally regarded as a plausible explanation as to why involuntary unemployment has persisted in the labor market. The standard or rudimentary efficiency wage model proposed by Yellen [1] 10 is the simplest version of the theory11. Its essential feature is that the effort function is directly specified without providing any micro-foundation by examining workers’ optimization behavior. This rudimentary type of efficiency wage model is always used as the analytical framework to illustrate the essential reason why wages do not fall to clear the labor market in the presence of mass unemployment. Some authors have used the standard efficiency wage model to explore various economic issues, such as Schmidt-Sørensen [18] [19] ; and the static model of the efficiency wages can be easy to extend to a dynamic model such as Lin and Lai [20] , Faria [21] [22] , Jellal and Zenou [23] [24] .
Let us consider a monopsonistic firm hiring a number of workers to produce a single product. The firm chooses the number of employees (n) and the wage (w) to maximize its profit (
), subject to the condition that the quantity of labor demanded (n) must not more than the quantity of labor supplied
in the labor market. That is:
(1)
(2)
The effort function








2.1. The Robinson Monopsony
For ease of comparison, Robinson’s monopsony can be regarded as an extreme case of this standard efficiency wage model when




This result


In this case, the monopsonistic firm’s optimization problem is to choose its optimal employment (n or N) to maximize



where




Equation (5) can be expressed in another way as12:

This result is demonstrated in Figure 1. Equation (6) states that a profit-maximizing firm will set its optimal employment







As a result, we have already shown the well-known result in the monopsony model whereby a single buyer will pay its workers a wage


noting that the market equilibrium point (E) of employment and wage



Proposition 1: When the workers’ effort has nothing to do with their wage, then the labor market equilibrium will result in a state of full employment, and the firm will pay its employees a wage less than their marginal revenue product.
Why will the monopsonist pay a wage






creasing rate of the wage as the employment expands. Why, then, does the single labor buyer have to increase its wage offer as it expands its labor force? This is because the single firm pays marginal workers their reservation wage, and so the labor supply curve is binding (labor market exhibits full employment). In order to attract and hire each additional worker with a higher reservation wage “progressively higher wages have to be paid to all in order to attract fresh supplies of labour” (Robinson [1] ). Since all the employed workers are paid the same wage, an additional hire will drive up the wage of all infra-marginal workers by the amount of
12The second-order condition is satisfied since
cost of marginal workers is thus







Figure 1. Robinson’s monopsony.
2.2. The Standard Efficiency Wage Model
When



Equation (7) states that, given the wage, the quantity of labor is employed at the level where the marginal revenue product of labor



The firm’s notional number of workers employed


The




Moreover, the





Let the positively-sloping line










2.2.1. The Market Labor Supply Curve Is Not Binding
In Figure 2, the point of intersection (E) of



Figure 2. Excess supply of labor.








A question that naturally arises is why the firm does not cut its wage in the presence of unemployed workers who are willing to work as long as the market wage is higher than their reservation wage. Alternatively, why does the firm not cut the wage when the wage offer is higher than the marginal workers’ opportunity cost? In fact, the firm does intend to cut its wage if it is profitable. This becomes clear when we consider the convention-
al setting in monopsony where




well as a cost to a firm associated with paying a higher wage. The firm may find it is profitable not to cut its wage to eliminate the excess supply of labor.
From Equation (7), it is very easy to see that the optimal choice of the monopsonistic firm is to pay its workers a wage


Proposition 2: When workers’ effort is positively related to their wage, and if the labor market equilibrium is characterized by a state of involuntary employment, then the firm will pay its employees a wage (w) equals their marginal revenue product (MRP).
2.2.2. The Market Labor Supply Curve Is Binding
In Figure 3, the point (E) at which the







find a job at that wage. We thus have





In this labor shortage situation, the firm must take the constraint




Figure 3. Excess demand of labor.




Proposition 3: When workers’ effort is positively related to their wage, and if the labor market equilibrium is characterized by a state of full employment, then the firm will pay its employees a wage that is less than their marginal revenue product.
Summarizing the above three propositions, we conclude that regardless of whether workers’ productivity is positively related to their wage or not, the firm pays them


In sum, according to the conventional wisdom that the result of

3. Conclusions
By using a simple standard efficiency wage model of Yellen [2] , this paper explores this conventional wisdom. Just as in the case of Robinson’s monopsony, the setting of this standard efficiency wage model is that there is a single firm and the firm has the market power to set the wage. Differences from Robinson’s monopsony in which the labor market equilibrium must be in full employment, the equilibrium may be characterized by either full employment or involuntary unemployment in this standard efficiency wage model. This paper finds that the single firm pays



At first glance, this result is confusing and presents us with a conundrum. Further inspection indicates that the reason for



If the labor supply curve is not binding (i.e. there is an involuntary unemployment), the firm can hire an additional worker without incurring the extra cost. The firm does not need to generate a gap between the marginal workers’ marginal revenue product and the wage to pay the extra cost. Without the extra burden, any gap between the wage and the marginal revenue product implies a potential profit that is not yet arbitraged; the firm will expand employment until



The finding, that the firm exploits workers when there is full employment but does not exploit them when there are involuntary unemployed workers, is obviously paradoxical. We therefore conclude that the key feature of

4. A Final Comment
Finally, I agree with Manning [4] ’s perspective that “[a] ssuming labor markets are monopsonistic also brings the thinking of labor economists in line with the way in which agents perceive the workings of labor markets”. I also believe Manning [4] ’s argument “that our understanding of labor markets is markedly improved by explicit recognition of the fact that employers have some market power in the determination of wages”. In fact, an increasing number of recent studies have been devoted to exploring the potential implications of monopsony15. Those who are familiar with the recent monopsony literature may expect that the importance of this paper’s finding (i.e. a monopsonistic firm may pay workers


Cite this paper
Chung-ChengLin, (2015) Exploitation in Monopsony. Theoretical Economics Letters,05,494-502. doi: 10.4236/tel.2015.54058
References
- 1. Robinson, J. (1933) The Economics of Imperfect Competition. MacMillan, London.
- 2. Yellen, J.L. (1984) Efficiency Wage Models of Unemployment. American Economic Review Proceedings, 74, 200-205.
- 3. Boal, W.M. and Ransom, M.R. (1997) Monopsony in the Labor Market. Journal of Economic Literature, 35, 86-112.
- 4. Manning, A. (2003) Monopsony in Motion: Imperfect Competition in Labour Markets. Princeton University Press, Princeton.
- 5. Baskar, V., Manning, A. and To, T. (2002) Oligopsony and Monopsonistic Competition in Labor Markets. Journal of Economic Perspectives, 16, 155-174. http://dx.doi.org/10.1257/0895330027300
- 6. Ashenfelter, O.C., Farber, H. and Ransom, M.R. (2010) Labor Market Monopsony. Journal of Labor Economics, 28, 203-210. http://dx.doi.org/10.1086/653654
- 7. Benson, A. (2013) Firm-Sponsored General Education and Mobility Frictions: Evidence from Hospital Sponsorship of Nursing Schools and Faculty. Journal of Health Economics, 32, 149-159. http://dx.doi.org/10.1016/j.jhealeco.2012.09.002
- 8. Cahuc, P. and Laroque, G. (2014) Optimal Taxation and Monopsonistic Labor Market: Does Monopsony Justify the Minimum Wage? Journal of Public Economic Theory, 16, 259-273. http://dx.doi.org/10.1111/jpet.12063
- 9. Gangopadhyay, P. and Shankar, S. (2015) Labour (Im)Mobility and Monopsonistic Exploitation of Workers in the Urban Informal Sector: Lessons from a Field study. Urban Studies, in press. http://dx.doi.org/10.1177/0042098015571056
- 10. Pigou, A.C. (1960) The Economics of Welfare. Macmillan, London.
- 11. Rottenberg, S. (1956) The Baseball Players’ Labor Market. Journal of Political Economy, 64, 242-258. http://dx.doi.org/10.1086/257790
- 12. Gilroy, T.P. and Madden, P.J. (1977) Labor Relations in Professional Sports. Labor Law Journal, 27, 768-776.
- 13. Downward, P., Dawson, A. and Dejonghe, T. (2009) Chapter 1—The Economics of Sport. Sports Economics, 1-33. http://dx.doi.org/10.1016/b978-0-7506-8354-8.00001-6
- 14. Scully, G.W. (1974) Pay and Performance in Major League Baseball. American Economic Review, 64, 915-930.
- 15. Medoff, M.H. (1976) On Monopsonistic Exploitation in Professional Baseball. Quarterly Review of Economics and Business, 16, 113-121.
- 16. Raimondo, H.J. (1983) Free Agents’ Impact on the Labor Market for Baseball Players. Journal of Labor Research, 4, 183-193. http://dx.doi.org/10.1007/BF02685176
- 17. Sommers, P.M. and Quinton, N. (1982) Pay and Performance in Major League Baseball: The Case of the First Family of Free Agents. Journal of Human Resources, 17, 420-436. http://dx.doi.org/10.2307/145589
- 18. Schmidt-Sorensen, J.B. (1990) The Equilibrium Effort-Wage Elasticity in Efficiency-Wage Models. Economics Letters, 32, 365-369. http://dx.doi.org/10.1016/0165-1765(90)90030-5
- 19. Schmidt-Sorensen, J.B. (1991) An Efficiency-Wage-Hours Modeland Shorter Working Hours. Scottish Journal of Political Economy, 38, 113-131. http://dx.doi.org/10.1111/j.1467-9485.1991.tb00305.x
- 20. Lin, C.C. and Lai, C.C. (1994) The Turnover Costs and the Solow Condition in an Efficiency Wage Model with Intertemporal Optimization. Economics Letters, 45, 501-505. http://dx.doi.org/10.1016/0165-1765(94)90094-9
- 21. Faria, J.R. (2000) Supervision and Effort in an Intertemporal Efficiency Wage Model: The Role of the Solow Condition. Economics Letters, 67, 93-98. http://dx.doi.org/10.1016/S0165-1765(99)00239-6
- 22. Faria, J.R. (2004) The Effects of Taxes on Labour in a Dynamic Efficiency Wage Model. Japanese Economic Review, 55, 286-297. http://dx.doi.org/10.1111/j.1468-5876.2004.00278.x
- 23. Jellal, M. and Zenou, Y. (1999) Efficiency Wages and the Quality of Job Matching. Journal of Economic Behavior & Organization, 39, 201-217. http://dx.doi.org/10.1016/S0167-2681(99)00032-3
- 24. Jellal, M. and Zenou, Y. (2000) A Dynamic Efficiency Wage Model with Learning by Doing. Economics Letters, 66, 99-105. http://dx.doi.org/10.1016/S0165-1765(99)00185-8
- 25. Akerlof, G.A. and Yellen, J.L. (1986) Introduction. In: Akerlof, G.A. and Yellen, J.L, Eds., Efficiency Wage Models of the Labor Market. Cambridge University Press, Cambridge, 1-21. http://dx.doi.org/10.1017/CBO9780511559594.001
- 26. Katz, L.F. (1986) Efficiency Wage Theories: A Partial Evaluation. NBER Macroeconomics Annual, 1, 235-276. http://dx.doi.org/10.2307/3585171
- 27. Solow, R. (1979) Another Possible Source of Wage Stickiness. Journal of Macroeconomics, 1, 79-82. http://dx.doi.org/10.1016/0164-0704(79)90022-3
- 28. Leibenstein, H. (1957) Economic Backwardness and Economic Growth. Wiley, New York, 58-67.
- 29. Akerlof, G.A. (1982) Labor Contracts as Partial Gift Exchange. The Quarterly Journal of Economics, 97, 543-569. http://dx.doi.org/10.2307/1885099
- 30. Weiss, A. (1980) Job Queues and Layoffs in Labor Markets with Flexible Wages. Journal of Political Economy, 88, 526-538. http://dx.doi.org/10.1086/260884
- 31. Shapiro, C. and Stiglitz, J.E. (1984) Equilibrium Unemployment as a Worker Discipline Device. American Economic Review, 74, 433-444.
- 32. Salop, S. (1979) A Model of the Natural Rate of Unemployment. American Economic Review, 69, 117-125.
- 33. Hyde, C.E. and Perloff, J.M. (1994) Can Monopsony Power be Estimated? American Journal of Agriculture Economics, 76, 1151-1155. http://dx.doi.org/10.2307/1243408
- 34. Boal, W.M. (1995) Testing for Employer Monopsony in Turn-of-the-Century Coal Mining. RAND Journal of Economics, 26, 519-536. http://dx.doi.org/10.2307/2556001
- 35. Hirsch, B.T. and Schumacher, E.J. (1995) Monopsony Power and Relative Wages in the Labor Market for Nurses. Journal of Health Economics, 27, 768-776. http://dx.doi.org/10.1016/0167-6296(95)00013-8
- 36. Hirsch, B.T. and Schumacher, E.J. (2004) Classic Monopsony or New Monopsony? Searching for Evidence in Nursing Labor Markets. IZA Discussion Papers No. 1154.
- 37. Azzam, A. (1996) Testing the Monopsony-Inefficiency Incentive for Backward Integration. American Journal of Agricultural Economics, 78, 585-590. http://dx.doi.org/10.2307/1243276
- 38. Green, F., Machin, S. and Manning, A. (1996) The Employment Size-wage Effect: Can Dynamic Monopsony Provide an Explanation? Oxford Economic Papers, 48, 433-455. http://dx.doi.org/10.1093/oxfordjournals.oep.a028577
- 39. Pauly, M.V. (1998) Managed Care, Market Power, and Monopsony. Health Services Research, 33, 1439-1460.
- 40. Staiger, D., Spetz, J. and Phibbs, C. (1999) Is there Monopsony in the Labor Market? Evidence from a Natural Experiment. NBER Working Paper No. 7258.
- 41. Baskar, V. and To, T. (1999) Minimum Wages for Ronald McDonald Monopsonies: A Theory of Monopsonistic Competition. Economic Journal, 109, 190-203. http://dx.doi.org/10.1111/1468-0297.00427
- 42. Manning, A. (2003) The Real Thin Theory: Monopsony in Modern Labour Markets. Labour Economics, 10, 105-131. http://dx.doi.org/10.1016/S0927-5371(03)00018-6
- 43. Manning, A. (2004) Monopsony and Efficiency of Labour Markets Interventions. Labour Economics, 11, 145-163. http://dx.doi.org/10.1016/j.labeco.2003.09.003
- 44. Manning, A. (2006) A Generalised Model of Monopsony. Economic Journal, 116, 84-100. http://dx.doi.org/10.1111/j.1468-0297.2006.01048.x
NOTES
1For same reason, in another survey paper, Bhaskar, Manning and To [5] suggest that the term monopsony “is best to think in terms of ‘oligopsony’ or ‘monopsonistic competition’ as the most accurate descriptions of the labor market”.
2There are many recent studies involving the labor monopsony model, for examples, Ashenfelter et al. [6] , Benson [7] , Cahuc and Laroque [8] , and Gangopadhyay and Shankar [9] .
3Robinson [1] defines “exploitation” as “[w] hat is actually meant by exploitation is, usually that the wage is less than the marginal revenue of labour…”. For further discussions, see Chapter 25 of Robinson [1] .
4Robinson [1] also refers to “the type of exploitation which arises because the supply of labour is imperfectly elastic to the unit of control”. 5Alternatively, Robinson [1] points out “exploitation occurs as a result of imperfection in the supply of labour”.
Prior to the 1970s, professional athletes (baseball, basketball, and football) faced significant restrictions on their mobility. The uniform contract contained a reserve clause that virtually bound the player to his team. The reserve clause permitted the team to renew the player’s contract unilaterally year after year, or to transfer him to another team in exchange for cash or another player. Under the reserve system, team owners enjoyed considerable monopsony power; players either had to bargain with the team holding their contracts or leave professional sports. In 1976, a new contract was signed in major league baseball, which made it easier for players to become free agents. Free agency provides players with the opportunity to sell themselves to the highest bidder. This and other later developments have lessened the monopsony power of the team. See Rottenberg [11] , and Gilroy and Madden [12] for further discussion. In a recent textbook regarding sports economics, Downward et al. [13] used the monopsony model as the framework to explain why players may be exploited.
6Scully [14] and Medoff [15] have indicated that labor market restrictions led to the exploitation of professional baseball players. Raimondo [16] , and Sommers and Quinton [17] have found that the removal of these restrictions resulted in salaries reflecting a baseball player’s value to his team (team worth).
7See Manning [4] for further discussions.
8The key difference between this simple standard efficiency wage model and Yellen’s is that a single firm setting is adopted in this paper to simplify the many identical firms assumption in Yellen’s. Supposing that there are many identical firms in this model will make the analysis a little more complex without altering the conclusion. Since the original Robinson monopsony is a single firm model, for the sake of comparison, this paper assumes there is only a single firm.
9Excellent surveys of the efficiency wage literature, see Yellen [2] , Akerlof and Yellen [25] , and Katz [26] .
10The same model is used in the survey paper of Akerlof and Yellen [25] . A cost-minimizing version of the standard efficiency model is constructed earlier by Solow [27] .
11Other more sophisticated versions of efficiency wage theory include nutritional concerns (Leibenstein [28] ), morale effects (Akerlof [29] ), adverse selection (Weiss [30] ), the shirking problem (Shapiro and Stiglitz [31] ), and labor turnover (Salop [32] ).
13The term “notional level” here refers to the firm’s optimal levels of labor demanded and wage offer without taking into account the resource constraint in Equation (2). When the constraint is not binding, the notional level will be the realized level, too; otherwise, they will not the same. For further discussions, see the following analysis.
14This is a standard result in the efficiency wage models. For example, Yellen [2] and Akerlof and Yellen [25] have pointed out that: “Each firm should then optimally hire labor up to the point where its marginal product,


15Some relevant studies are listed as follows: Hyde and Perloff [33] , Boal [34] , Hirsch and Schumacher [35] [36] , Azzam [37] , Green, Machin and Manning [38] , Boal and Ransom [3] , Pauly [39] , Staiger, Spetz and Phibbs [40] , Bhaskar and To [41] , Baskar, Manning and To [5] , and Manning [4] [42] -[44] .
16See Manning [42] for a brief list of relevant applications.











