How does demand uncertainty affect firms' investment decisions? We examine this question in the context of electricity‐producing firms' planned investments in new power plants. We measure uncertainty about future electricity demand using plausibly exogenous variation in temperature projections across scientific climate models. The results show that uncertainty increases investment in power plants with flexible production technologies, while reducing investment in less flexible technologies. Overall, the net effect of uncertainty on investment is positive when firms have access to flexible investment opportunities. These findings are consistent with models in which production flexibility shapes the investment response to demand uncertainty.

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.