More so than any other sport, baseball is statistics driven. From RBIs to the WAR index, there is no other sport that measures more, or pays more attention to numbers.

Alan Hall, a senior analyst at the Socionomics Institute would like to add another acronym to baseball’s growing number of measurements: SWAT. More specifically the SWAT index, which tracks league-wide home runs and strikeouts per game.

This season, homers, strikeouts and SWAT are at all-time highs. And so is the stock market. Hall says players and investors alike are in the mood to swing for the fences.

“It comes down to social psychology. Social mood regulates trends on the trading floor and the baseball field,” he says. “When society is feeling more confident and optimistic, speculators express those feelings by bidding stock prices higher — and hitters express those feelings by swinging for the fences. When society is feeling more fearful and pessimistic, speculators and hitters are more inclined to engage in the opposite behaviors.”

Could it just be a coincidence? If so, it’s one that has persisted for more than a century. Hall studied 147 years of stats on Major League home runs and U.S. stocks and uncovered the surprisingly consistent connection between the two. He found an even better fit when he added strikeouts to the home run data to create the SWAT index.  

“Home runs are one indication that hitters are swinging for the fences. Strikeouts are another. All those big swings make it more likely hitters will miss. SWAT takes into account both indicators,” Hall explained.

Baseball metrics have come a long way in the past 40 years, but until now stats that give us a window into batter psychology and confidence have remained elusive.