A new study by Columbia Business School economists shows that the influence of news on financial markets is “often greater a year after the report than a month,” according to a recent article in Barron’s.

The study analyzed how stock markets in 51 countries reacted to “millions of news items written by Reuters over a 19-year period ended in 2015.” The researchers conclude that the delayed reaction to news occurs because “of the time it can take for investors to fully appreciate the ramifications of what they read about.”

Charles Calmoiris, one of the authors, concludes: “There is an undercurrent embedded in the news flow, but not in a way that investors can always discern. They’re looking at the trees, but there is a forest, and our research is shining light on that forest.”