| Abstract: | This article proposes a new model for autoregressive conditionalheteroscedasticity and kurtosis. Via a time-varying degreesof freedom parameter, the conditional variance and conditionalkurtosis are permitted to evolve separately. The model usesonly the standard Student’s t-density and consequentlycan be estimated simply using maximum likelihood. The methodis applied to a set of four daily financial asset return seriescomprising U.S. and U.K. stocks and bonds, and significant evidencein favor of the presence of autoregressive conditional kurtosisis observed. Various extensions to the basic model are proposed,and we show that the response of kurtosis to good and bad newsis not significantly asymmetric. |
