We analyze a multiple-activity, principal-agent model in which the activities are naturally substitutable for the agent and complementary for the principal. A basic result is that the optimal compensation must cause the agent to view the activities as complements. This complementarity is...

The evolution of technology causes human capital to become obsolete. We study this phenomenon in an overlapping generations setting, assuming that technology evolves stochastically and that older workers find updating uneconomic. Experience and learning by doing may offer the old some income...