New York CNN Business  — 

Executives of America’s large public companies have long played a role in public policy by advising leaders of both parties — but those corporate chieftains themselves are far more likely to be Republicans than Democrats, a new study shows.

In a working paper released this month by the National Bureau of Economic Research, researchers at Harvard Law School and Tel Aviv University ran the names of all individuals to have run a company listed in the S&P 1500 between 2000 and 2017 through federal campaign finance databases, which include contributions to both congressional and presidential candidates as well as party committees.

The result: 18.6% of CEOs consistently donated to Democrats, while 57.7% donated to Republicans, with the rest leaning toward neither party.

That may not be surprising, given how big business tends to benefit more from conservative policy goals like lowering taxes and easing up on regulations. Labor unions donate heavily to Democrats, who tend to support more worker-friendly policies.

But the research shows just how deep those preferences run, and it further explores the wider implications at a time when corporations spend vast sums of money on elections.

“Public corporations have massive financial resources, and directing even a tiny fraction of them to politics could have a profound impact,” the authors wrote. “In particular, because our evidence indicates that public companies are disproportionately headed by Republican CEOs, the emergence of such a scenario could have a significant impact on the balance of power and advantages between the two main political parties.”

The CEOs skewed even more Republican in certain industries, such as energy, as well as in the South and Midwest.

There was almost no partisan imbalance among female CEOs, who made up only 2.8% of those measured. Also, the prevalence of Republican-leaning donors declined over the 2000 to 2017 sample period, as more shifted to a neutral stance while the share of Democrats remained constant.

In terms of dollar value, less than a third of individual donations went to Democrats. The more important measure, however, may be the amount that their companies donate. That’s much more difficult to measure, because it’s often done through dark money groups that don’t have to disclose their donors. What’s more, the researchers found that companies run by Republican CEOs are meaningfully less transparent about their giving than those run by Democratic CEOs, judging by scores given by the Zicklin Center for Business Ethics Research at the University of Pennsylvania.

The study comes amid a growing body of academic work on the edge of political science and economics that examines the relationship between corporate actors and policy making. For example, another pair of recent papers by economists affiliated with the National Bureau of Economic Research examined how corporate money influences policy in more subtle ways.

One found that nonprofit organizations are more likely to submit comments during rulemaking processes that favor their corporate donors, increasing the likelihood that the final rule reflects their donors’ priorities. Another found that the philanthropic arms of Fortune 500 and S&P 500 companies funnel their contributions into the districts of members of Congress who attain seats on committees that are relevant to their industries, and concluded that the amount of politically motivated “charitable” giving amounted to more than six times the amount raised annually by political action committees.

“Given the lack of formal electoral or regulatory disclosure requirements, charitable giving may be a form of political influence that goes mostly undetected by voters and shareholders, and which is directly subsidized by taxpayers,” the authors wrote.