(Adds comment from State Street executive)
BOSTON, Sept 18 (Reuters) - Top U.S. asset managers took a slightly tougher line on executive pay in the advisory votes they cast at S&P 500 companies this year, a research firm said on Monday.
For the 12 months ended June 30, funds run by BlackRock Inc, Vanguard Group and State Street Corp each supported management recommendations on executive pay about 2 percentage points less frequently than in the same period a year earlier, researcher Proxy Insight said, based on a review of recent securities filings.
All three firms still cast their advisory compensation votes in favor of management nearly all the time. BlackRock funds, for instance, supported management on pay 96.4 percent of the time, down from 98.3 percent of the time the prior year and 99.3 percent of the time the previous year.
Voting by the other major firms followed a similar pattern.
But factored across thousands of fund votes, the results "suggest a structural reduction in investor support for pay at U.S. companies," Proxy Insight said in a news release.
"For the layman it's not a huge shift, but you can see there are more votes that are going against" management, said Nick Dawson, managing director of Proxy Insight.
In an e-mailed statement, Matthew DiGuiseppe, head of asset stewardship for the Americas at State Street's asset-management arm, said it tries to speak with company leaders before casting critical votes.
"However, when we feel that companies are not receptive to our concerns we will vote against the Say-on-Pay," he said.
Representatives from the other firms did not immediately comment. Each has previously said they review pay decisions in the context of factors like company performance.
A preliminary review by Proxy Insight had already found strong support for executive pay, even as the fund firms broke with management on matters like climate change and boardroom diversity.
The median S&P 500 CEO was paid $12.1 million last year, up from $11 million among the same group in the previous year, according to ISS Analytics.
(Reporting by Ross Kerber; Editing by Dan Grebler)