Efficient market hypothesis
The proposition that available information is already reflected in the price, so it cannot be used to beat the market systematically.
How to read the number
It comes in several versions differing in what counts as reflected: past prices, public data, or information of any origin whatsoever.
When the metric lies
No single example confirms or refutes it: a profitable trade is consistent with the hypothesis and a losing one is consistent with its denial.
Also known as: emh