In this article we derive conditions which ensure the non-negativity of the conditional variance in the Hyperbolic GARCH(p; d; q) (HYGARCH) model of Davidson (2004). The conditions are necessary and sufficient for p < 2 and sufficient for p > 2 and emerge as natural extensions of the inequality constraints derived in...</2>

We investigate the impact of the European Central Bank's monetary policy announcements on the level and volatility of the EUR-US Dollar exchange rate employing an AR-FIGARCH specification. Using high-frequency data we estimate the individual and complementary effects of the release of the...