Max Stevenson

Detecting and modelling nonlinearity in flexible exchange rate time series

The aim of this paper is to examine the appropriateness of nonlinear time series analysis as a framework in which to model the dynamics of exchange rates. This aim has been motivated by the questioning of the power of classical unit root tests, the accumulating amount of evidence which suggests that exchange rates follow some kind of nonlinear process, and the fact that standard asset pricing theories do not explain well the empirical observations of exchange rate movements. The paper has three major objectives. First, to test for the presence of unit roots in nominal exchange rate time series. Second, for those nominal exchange rate time series found to be stationary, to test for nonlinearity using both tests derived without a specific nonlinear alternative in mind and tests against a specific nonlinear model. Finally, we motivate the types of nonlinearity for which we test by examining a recently proposed nonlinear model of exchange rate dynamics.

Asymmetry in the business cycle: Evidence from the Australian labour market

Cyclical asymmetry has been recognised as a nonlinear phenomenonin recent studies examining unemployment rate time series. In this paper we use a number of established and new tests for identifying nonlinearities of the bilinear (BL), exponential autoregressive (EXPAR), smooth transition autoregressive (STAR), and self-exciting threshold autoregressive (SETAR) types as they occur in time series of the seasonally differenced logarithm of monthly Australian aggregate and regional unemployment rates. After identifying nonlinearity of a particular form within a given time series, the appropriate model is fitted and representations from the model analysed for their cyclical behaviour.