The Harvard Business Review recently did a peer review on a study by University of Michigan researchers:

“We find strong lunar cycle effects in stock returns,” say University of Michigan Business School professors Ilia D. Dichev and Troy D. Janes in a research report.

“Specifically, returns in the 15 days around new moon dates are about double the returns in the 15 days around full moon dates. This pattern of returns is pervasive,” they report.

The scholars set out to examine the folk wisdom that moon cycles affect human behavior, especially abnormal behavior around full moons. They turned to stock markets to get a big enough sample, as millions of people make billions of trades on a regular basis.

They gathered data on major U.S. stock markets over the past 100 years, and on the markets of 24 other nations going back 30 years.

“Taken as a whole, this evidence is consistent with popular beliefs that lunar cycles affect human behavior,” the researchers concluded.

The Harvard Business Review, reporting the research in its current issue, says that while these findings “are a bit off the beaten path, they’re the product of rigorous research.”

It’s hard to predict the ups and downs of individual stocks because there’s so much variability in the fortunes of companies and there are greater cycles that would also have an effect, such as the Jupiter/Saturn cycle we just experienced and the passage of Jupiter through Scorpio (expanding stocks/other people’s money) and now Jupiter in Sagittarius (more irrational exuberance). This is a trend that can’t be used for investing: for example, the stock market fell today even though a new moon is around the corner. But it does prove a correlation between moon cycles and human behavior that most of us are already familiar with.