Though essentially restatements of imperfect competition theories from the 1930s, the new Marxist and radical versions of monopoly capital were advanced to explain how market power served to prop up longstanding, above-average rates of profit. These rates were considered to be the sustaining lifeblood separating high-wage, primary markets from low-wage secondary markets. Interestingly, while reviving the importance of class struggle (once the centerpiece of classical political economy), many radicals were either ignorant of, or rejected outright, Marx's theory of the law of value. Marx considered this law as absolutely critical—it held the key to understanding the objective limits of a theory of inter and intra-industry profit and wage differentials tied to his dynamic theory of capitalist accumulation. With the lone exception of Howard Botwinick's contribution, Persistent Inequalities, no radical or Marxian work in labor economics has systematically broken away from the underpinnings of neoclassical theory, in either its perfect or imperfect versions, to formulate a theory of wage differentials consistent with Marx's law of value.
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