At JPMorgan's annual meeting last week, only 61 percent of votes cast endorsed the bank's executive compensation. Thirty-six percent backed plans to separate Dimon's dual position into multiple posts after he leaves.
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Dimon on Wednesday decried shareholders' perceived reliance on recommendations from Glass Lewis and Institutional Shareholder Services.
"God knows how any of you can place your vote based on ISS or Glass Lewis," Dimon said. "If you do that you are just irresponsible, I am sorry. And, you probably aren't a very good investor, either. I know some of you here do it because you are lazy."
McCormick contended that many mutual funds or pension funds use a variety of sources to inform voting decisions. He added that JPMorgan is a large enough company that shareholders need more information to take a stance on corporate issues.
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Calling institutional investors lazy is "harsh," said Dan Laddin, senior partner at executive pay consulting firm Compensation Advisory Partners, in a "Power Lunch" interview on Thursday. However, he noted that they "have an obligation to make an assessment on their own."
He added that, while larger investors may have the resources to evaluate proxy votes on their own, smaller operations often have to rely on firms such as CSS and Glass Lewis.
—Reuters contributed to this report.