Do heterogeneous expectations constitute a challenge for policy interaction?

Yes, indeed; at least when it comes to fiscal and monetary policy interaction. We examine a Neo-Classical economy, where agents have either rational or adaptive expectations. We demonstrate that the monetarist solution can be unique and stationary under a passive fiscal/active monetary policy regime, because active monetary policy incorporates expectational heterogeneity. In contrast, under an active fiscal/passive monetary policy regime, the fiscalist solution is prone to explosive dynamics d e to empirically plausible expectational heterogeneity. However, conditional on stationarity, both regimes can yield promising business cycle dynamics, which are absent in the homogeneous expectations benchmark.