This paper assesses empirically two competing unemployment theories. It identifies one structural break in U.K. and German unemployment around 1980 that is more severe in both absolute and relative terms than that for the United States in 1973. This offers support for the structuralist theory. A nonlinear (TAR) model is used to capture fast-up, slow-down unemployment dynamics. Impulse response functions suggest that the half-lives of shocks are longer in the postbreak subsamples, especially in Europe, which places the persistence theory closer to the mark. We conclude that elements from both theories are needed for an adequate account of unemployment dynamics.