A research study published last year in the Financial Analysts Journal found that net buybacks account for the bulk of the intermediate- and longer-term differences in stock market returns around the world. This according to a recent Wall Street Journalarticle by columnist Mark Hulbert.

“This comes as a surprise,” Hulbert writes, “because the conventional wisdom is that economic growth is by far the most important factor in the outperformance of certain countries’ stock markets in recent decades. The researchers,” he adds, “found little support for this belief.”

The study, which involved an analysis of 43 countries’ stock markets between 1997 and 2017, found that the best performers were, on average, those with lower economic growth rates. Similarly, Hulbert explains, they found that “variances in countries’ equity returns had little to do with any of the other usual suspects to which analysts often turn when trying to account for varying equity returns, such as inflation, currency fluctuations and profit margins.” Across the board, the study found that net buybacks dominated all other factors—specifically, that they explained 80% of the difference in returns over the two-decade period.

According to TrimTabs director of liquidity research David Santschi, the clear implication is that “other things being equal—the U.S. stock market’s expected future return will be lower if buybacks are restricted.” He recommends regulatory changes that would make it easier for investors to track corporate buyback activity.