Weak-form efficiency

If a market is weak-form efficient, a strategy based solely on past price and volume patterns should not consistently earn abnormal risk-adjusted returns after costs. This challenges chartism as a dependable excess-return method, but does not assert that all public fundamental information or private information is already incorporated. New information can still move prices, and some investors may outperform by chance. Test claims against appropriate risk and cost benchmarks rather than confusing a positive absolute return with an abnormal return.