... is that the more data you have, the morecomplete the picture you can draw from your backtesting results. Wayne A. Thorp is assistant financial analyst of AAII.AAII Journal/January 2001 31 TECHNICAL ... 30 AAII Journal/January 2001 TECHNICAL ANALYSIS By Wayne A. Thorp Many forces are atwork when you trade a system—commissions,slippage, protectivestops, idle interest,margin, and shorttrading ... historical database.Ideally, whenever you backtest a system, you want to use a “significant”amount of data in order to capture as many different market phases aspossible. The amount of data you...