The principal can limit divergences from his interest by establishing appropriate incentives for the agent and by incurring monitoring costs designed to limit the aberrant activities of the agent.

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That is held to result when the market suffers from inadequate or inaccurate information delivery, inadequate or insufficient competition, principal-agent problems (where agents fail to represent the interests of their principals), and externalities (where market actors fail to bear the costs of their actions or choices), among other problems.

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In terms preferred by economists, a situation defined by a principal-agent problem (such as you hiring a doctor or car mechanic who gets to both define your problem and figure out what to charge you for fixing it) was replaced by a much simpler employment relationship: would-be hustlers found themselves being turned into professional, generalist managers.

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