Many of the nation’s largest publicly traded companies are disclosing more information about their political contributions, according to a study released Thursday.

More corporations are also placing restrictions on political spending to candidates, parties, committees and so-called “dark money” groups, according to the report from the Center for Political Accountability, a nonpartisan group that promotes greater transparency in corporate political spending.

The move toward more transparency is happening at a time when political spending from outside groups is on a dramatic upswing — and is expected to reach a record high for the 2016 presidential election — following the Supreme Court’s 2010 decision in Citizens United, which allows corporations and unions to spend unlimited amounts of money in direct advocacy for or against candidates.

“There’s been a steady growth of companies recognizing that disclosure and accountability are good practices and are important for risk management,” said the study’s author Bruce Freed, president of the Center for Political Accountability.

The group began engaging corporations on political spending in 2003 and started publishing an annual study in 2011. The study rates companies on a scale of 0 to 100 based on their policies for disclosing political spending as reported on their corporate websites. The survey is done in conjunction with the Zicklin Center for Business Ethics Research at the University of Pennsylvania’s Wharton School of Business.

The report has surveyed an increasing number of companies each year and it tracks subsequent improvement by those companies. This year, for the first time, the study looks at all the companies in the S&P 500.

Among the 83 companies surveyed since 2011, the average score rose from 45.2 to 71.3 in 2015.

Among the 186 companies surveyed since 2012, the average score rose from 38.1 to 59.4 in 2015.

Among the S&P 300 companies that were evaluated in 2014, the average score rose from 47.5 to 50.4

The companies that received the highest ratings in 2015 were medical technology company Becton, Dickinson and Co.’ railway supplier and operator CSX Corp., and Noble Energy Inc., which each received a score of 97.1.

About half of the companies in 2015 disclosed some information about their contributions to candidates, parties and committees or have policies prohibiting such contributions. Forty-one percent of the companies disclosed information about their contributions to influence ballot measures or had policies against engaging in such activities. Forty-one percent of the companies disclosed information about payments to trade associations or instructed trade associations not to use the contributions on election-related activities.

About 25 percent of the companies placed some restrictions on political spending, including on contributions to candidates, parties, committees, ballot measures, 501(c)(4) groups and payments to trade associations for political purposes.

“This is a major change since 2004 when few companies imposed such restrictions, or had policies about how they would spend on politics,” the study said.

The Center for Political Accountability supports efforts by Senate Democrats who are pressing the Securities and Exchange Commission to require publicly traded companies to disclose their political spending.