Rather than look at party affiliation or public statements, the researchers — Alma Cohen, Moshe Hazan, Roberto Tallarita and David Weiss — looked at the truest measure of political leanings: They followed the money.

For the study, to be released Tuesday, they tracked personal political contributions for more than 3,500 chief executives that occupied the corner office anytime from 2000 to 2017 . The period covers a two-term Republican presidency, a two-term Democratic presidency and the start of President Trump’s time in office — after he lost the popular vote but won the Electoral College. In other words, on the whole, voters have been pretty evenly divided between the parties in that time.

But just 18.4 percent of the executives studied were designated as Democrats. The clear majority — 57.7 percent — demonstrated their affiliation through donations to the Republican Party. Indeed, 75 percent of donations from the median chief executive were directed to Republicans.

To be counted a supporter of Republicans or Democrats, executives had to direct at least two-thirds of their donations to candidates affiliated with one party. More than a quarter of the executives studied gave enough to both parties to be classified as “neutral.” This was the landing spot of Tim Cook, the chief executive of Apple. Despite his public support for Hillary Clinton in the last election and his backing of a number of progressive causes, he frequently gave money to candidates on both sides of the aisle.

(Unfortunately, the researchers have not disclosed how they classified each executive, saying they wanted to focus on the whole, and not the parts. When I asked for an example, they provided me with Mr. Cook.)