The Limits of p‐Hacking: Some Thought Experiments

Suppose that the 300+ published asset pricing factors are all spurious. How much p‐hacking is required to produce these factors? If 10,000 researchers generate eight factors every day, it takes hundreds of years. This is because dozens of published t‐statistics exceed 6.0, while the corresponding p‐value is infinitesimal, implying an astronomical amount of p‐hacking in a general model. More structure implies that p‐hacking cannot address ≈100 published t‐statistics that exceed 4.0, as they require an implausibly nonlinear preference for t‐statistics or even more p‐hacking. These results imply that mispricing, risk, and/or frictions have a key role in stock returns.