Summary.
The belief that lunar cycles affect how we think and act is widespread and old as the hills, yet, understandably, scholars have struggled to find evidence to support it. That’s not necessarily because the belief isn’t valid, suggest Ilia D. Dichev of the University of Michigan and Troy D. Janes of SUNY Buffalo; the problem could be that many studies examine extreme behavior and thus work with small samples. So for their own research, Dichev and Janes turned to stock markets, where hundreds of millions of people make countless decisions daily. After all, they point out, if a full moon brings on depression and pessimism, as legend has it, mightn’t it trigger a gloomy outlook about future cash flows, leading to risk-averse investing and causing stock prices—and returns on investments—to tank?