Before revision: We demonstrate that if all agents in an economy make time-consistent decisions and policies, then there exists no rational expectation equilibrium in a dynamic stochastic general equilibrium (DSGE) model, unless under very restrictive and special circumstances. Some time-consistent interest rate rules, such as Taylor rule, worsen the equilibrium non-existence issue in general circumstances. Monetary policy needs to be lagged in order to avoid equilibrium non-existence due to agents making time-consistent decisions. We also show that due to the transversality condition issue , either fiscal-monetary coordination may need to be modeled, or it may be necessary to write a model such that bonds or money provides utility as medium of exchange or has liquidity roles .
After revision: We demonstrate that if all agents in an economy make time-consistent decisions and policies, then there exists no rational expectation equilibrium in a dynamic stochastic general equilibrium models induced by consumer heterogeneity, in contrast to static models. However, one can consider REE-prohibiting initial conditions as limits of other initial conditions. The REE existence issue then is overcome by using a limit of economies. This shows that significant care must be taken of when dealing with rational expectation equilibria .