Abstract
New evidence is presented on the positive correlation between returns from technical trading rules and periods of central bank intervention. To that end, the profitability of a trading strategy based on nearest-neighbour (nonlinear) predictors is evaluated, which may be viewed as a generalization of graphical methods widely used in financial markets. Daily data on the US dollar/Deutschmark and US dollar/Japanese Yen covering the 1 February 1982–31 December 1996 period are used. The results suggest that the exclusion of days of US intervention implies a substantial reduction in all profitability indicators (net returns, ideal profit measure, Sharpe ratio and directional forecast), being the reduction grater in the US dollar-Deutschmark case than in the US dollar-Japanese yen case.