The U.S. Capitol stands in Washington, D.C., U.S., on Wednesday, Sept. 27, 2017. A new study on corporate political spending shows an increase in disclosure and oversight among the largest publicly traded companies. (Andrew Harrer/Bloomberg)

Major public companies are letting a little more sunlight into their wallets, making more disclosures about their political spending on their web sites and adding more board oversight to monitor it, according to a new study.

The report released Tuesday, by the nonpartisan Center for Political Accountability and researchers at the University of Pennsylvania's Zicklin Center for Business Ethics Research, creates an index that ranks companies based on the disclosure, oversight and policies about their election-related spending. It found that 50 companies in the S&P 500 received scores of 90 percent or above, up from just 41 companies in 2016 and 28 in 2015.

More companies had specific board committees that review political expenditures and payments to trade associations, the study found. And more placed limitations on the kinds of political spending they allow, with 158 placing restrictions this year, up from 143 in 2016. "As we move into the Trump presidency, you see a growing company embrace of political disclosure and accountability," said Bruce Freed, president of the Center for Political Accountability. "That's the key finding. There's been no retreat."

The rising trend in disclosure comes at a time when the push to get the Securities and Exchange Commission to adopt political disclosure rules has stalled, even as the Citizens United Supreme Court case loosened restrictions on corporate political spending in 2010.

At the same time, CEOs are increasingly engaging in political and social issues, driven by the demands of employees and customers who increasingly want to know more about the political positions and values of the companies they do business with. More and more, Freed said, investors also see political spending as a risk management issue. For instance, companies that speak out publicly about climate change or LGBTQ rights -- but give to groups out of line with those ideas -- could put themselves at risk in today's vigilant social media world.

"Companies are paying much more attention to what they’re associated with and what they don’t want to be associated with," Freed said. "Social media can amplify that."

The study ranks companies based on the information they provide on their web sites about factors such as payments to super PACs and tax-exempt organizations like 501(c)(4)s, whether or not senior managers or board members oversee political spending and activities, and what kind of policies they outline for how and where money can be spent.

"What we hear from companies is that policies give them the ability to say no and not have the fear that it appears personal," said Freed, whose organization has also spearheaded a campaign of shareholder resolutions to get boards to sign on to greater disclosure. (The index does not examine lobbying spending as part of its analysis.)

One company in this year's study, which has ranked the S&P 100 since 2011 and the S&P 500 since 2015, stood out for a notable first: The medical technology company Becton, Dickinson received the index's first 100 percent score by a company that did not already have a ban on election-related corporate spending, which allows companies to score well by default. Companies including State Street Corp., Microsoft and Morgan Stanley also appear in the top 10.

Nine other companies saw at least a 50-point increase in their scores, including Host Hotels & Resorts, Ralph Lauren, Synchrony Financial and Newell Brands. Industries with stricter regulatory ties like utilities and health care tended to score higher, as did larger companies, which tend to have more resources to disclose their spending and often, stronger governance practices.

But 59 companies remain what Freed calls "basement dwellers," or those with a score of zero. Companies may have a low score simply because they don't make political contributions -- and don't reveal that information on their web site -- or because they choose not to disclose information for competitive reasons. Dish Network and E-Trade Financial are two that score a zero.

One critic of the index is the Center for Competitive Politics' Brad Smith, a former Federal Election Commission chair who says much political spending by corporations is already disclosed and that the index is a "one-size-fits-all" model that does not necessarily have corporations' best interests at heart. He suggests those behind the index "tend to think corporate involvement is a bad thing -- they want to get corporations not to participate. But most Americans, I think, believe corporations do have a role to play in terms of politics."

Freed, whose organization reaches out to companies before they post the index, says they do not make judgments about companies' political spending, they just want to see companies disclose it themselves, and have clear policies and strong oversight measures in place. "Just describe what you do and what you don't do," he says, noting that consolidating information in one place can be helpful to investors and to managers for monitoring and decision-making.

Eight companies among the S&P 500 don't use corporate assets for election-related spending at all, the report says, including Accenture, IBM and Schlumberger.

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