Bulls and Bears: Heterogeneous Expectations

“It is differences in opinion that makes horse races”, Mark Twain says. Following this saying, I study differences in ex­pectations among agents in this chapter. Agents conform that the state of the world is described by a diffusion model as in Chapter 1. They differ, however, in their prior beliefs about some unknown parameters of the model. To give an example, the drift of the growth rate may be unknown, as in the pre­ceding chapter, and some agents, call them bulls, might hold more optimistic views about this drift than others.