“…Using nonparametric techniques, the seminal paper of Neftci (1984) finds unemployment rises to be sudden, and falls to be gradual; see also Sichel (1989) and Rothman (1991). Various parametric nonlinear time series models of unemployment have also been estimated in the literature by Hansen (1997), Bianchi and Zoega (1998), Koop and Potter (1999), Papell et al (2000), Caner and Hansen (2001), Skalin and Teräsvirta (2002), Coakley and Fuertes (2006), Caporale and Gil-Alana (2007), among others. All these studies assume Markov-switching, threshold or smooth transition specifications.…”