Ladislaus von Bortkiewicz (1868 - 1931) was a European statistician. His scientific work covered theoretical economics, stochastics, mathematical statistics and radiology, today we would call him a cross disciplinary scientist. With his clear views on mathematical principles with their...

This paper offers a new method for estimation and forecasting of the volatility of financial time series when the stationarity assumption is violated. Our general, local parametric approach particularly applies to general varying-coefficient parametric models, such as GARCH, whose coefficients...