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Stats › Backtesting and evidence › Machine learning

The best machine learning forecast explains 0.40% of monthly return variance

Elastic net
0.11%
Least squares, 3 predictors
0.16%
Generalised linear model
0.19%
Principal components
0.26%
Partial least squares
0.27%
Random forest
0.33%
Boosted trees
0.34%
Neural network, three layers
0.40%

Monthly out of sample R squared for individual stock return forecasts, all stocks, out of sample window 1987 to 2016 with annual refitting. The benchmark is a forecast of zero rather than the historical mean, which mechanically raises every figure. Unregularised least squares on all 920 predictors is omitted here and scores minus 3.46%.

Neural network forecasts produced a monthly out of sample R squared of 0.40% and a long short Sharpe ratio of 1.35 value weighted and 2.45 equal weighted. Neither of the two most cited studies reports any transaction cost adjustment at all.

0.40%Best monthly out of sample R squared across all methods
0.16%The same for a three predictor linear model
-3.46%The same for unregularised least squares on 920 predictors
NonePublished cost adjusted Sharpe ratios located

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