Modeling diverse expectations in an aggregated New Keynesian Model

We explore a New Keynesian Model with diverse beliefs and study the aggregation problems in the log-linearized economy. We show the solution of these problems depend upon the belief structure. Agents' beliefs are described by individual state variables and satisfy three Rationality Axioms, leading to the emergence of an aggregate state variable named “mean market state of belief.” In equilibrium, endogenous variables are functions of mean market belief and this state variable is the tool used to solve the aggregation problems.