Dynamic Asymmetries in U.S. Unemployment.

The authors examine dynamic asymmetries in U.S. unemployment using nonlinear time series models and Bayesian methods. They find strong statistical evidence in favor of a two-regime threshold autoregressive model. Empirical results indicate that, once parameter and model uncertainty are both taken into account, there are economically interesting asymmetries in the unemployment rate. One finding of particular interest is that shocks that lower the unemployment rate tend to have a smaller effect than shocks that raise the unemployment rate. This finding is consistent with unemployment rises being sudden and falls gradual.