Here’s a very slightly modified version of a comment that I left on a nice post by Scott Sumner at EconLog :
Nice post. I add four points that I’ve made in the past at my blog.
First, as Jim Buchanan , Donald Dewey , and other economists have pointed out, as long as demand curves for outputs are downward sloping, monopsony power is only a necessary and not a sufficient condition for minimum wages not to reduce the employment prospects of low-skilled workers. For minimum wages not to reduce these workers’ employment prospects, employers with monopsony power must also have monopoly power (and not just the sort of such ‘power’ as is identified in models of monopolistic competition). That is, these employers must have the ability to keep the prices of the outputs they sell above average total costs. If they do not have this ability, then there are no excess profits, or rents, out of which the higher labor costs can be paid.
Second, empirical studies typically fail to examine all the many ways that employers and employees can adjust to minimum wages. The list of such possible adjustments other than reduced hours of employment includes reductions in formal fringe benefits (such as paid leave), reductions in informal fringe benefits (such as workplace safety higher than what is minimally required by legislation), and changes in the nature of the jobs such that workers are worked harder in order to produce more output per hour. To the extent that adjustments such as these occur, minimum-wage-induced reductions in employment will be fewer or lower, but the standard textbook model really still holds.
Third, because in the U.S. the national minimum wage has been in place now for 80 years and is at no risk of being repealed, employers have long ago adjusted their business plans – their capital-labor ratios – to the existence of minimum wages. And employers expect occasional minimum wage increases. Therefore, even the finest and most carefully controlled empirical study of a minimum-wage hike today will not detect the employment-reducing effects of the long-standing expectation of minimum-wage hikes. Because employers have already adjusted to the reality of minimum wages – and to the reality of minimum wages being increased from time to time – any study that correctly finds little or no negative employment effect from this or that minimum-wage hike today nevertheless misses the negative employment effects of minimum wages overall.
Fourth, about monopsony power: it’s more difficult to detect than, ironically, standard textbook models suggest. Suppose that Acme, Inc., competes for workers by offering unusually attractive fringe benefits and work conditions. And suppose that Acme, Inc., has a differential advantage over other employers at supplying to its workers such non-wage amenities, or that for Acme, Inc., the marginal cost of attracting X number of workers by supplying non-wage amenities is lower than is its cost of attracting X number of workers by increasing the wages it pays. Under such conditions, Acme, Inc., gains the power to lower its workers wages by some amount without losing all, or perhaps even any, of its workers.
An empirical study of this firm would conclude that Acme, Inc., has monopsony power. But this conclusion would be incorrect, for the ‘power’ that Acme, Inc., is detected to have over its workers is ‘power’ that Acme, Inc., purchased from its workers – workers who voluntarily agreed to Acme’s employment terms.
Put differently, if (as is not unreasonable for many employers) Acme, Inc., values a steady workforce, it can purchase – with non-wage amenities – from its workers the ability to cut their wages without their quitting. The textbook-bound economist, seeing only the reduced wages and no mass exodus of workers from Acme, leaps confidently to the conclusion that Acme has monopsony power. Yet clearly, in this example, that conclusion would be mistaken.