Zaffaroni, Paolo - Suntory and Toyota International Centres for Economics … - 2000
Sufficient conditions for strict stationarity of ARCH(8) are established, without imposing covariance stationarity and …-negativity constraints are imposed. Second, we show the necessary and sufficient conditions for covariance stationarity of ARCH(8), both for … the levels and the squares. These prove to be much stronger than the strict stationarity conditions. The covariance …