"We heard the same refrain: We have learned from our mistakes. This will never be allowed to happen again," Finn said. "I can't help wondering if you are listening."
Lisa Lindsley, director of capital strategies for an influential union of public employees that is also a major JPMorgan shareholder, said independent board leadership was in shareholders' best interest.
"An all-powerful CEO is his own boss," she said. "Looking for an infallible CEO is a fool's errand."
Most large American companies combine the jobs of chairman and CEO, but shareholders have pushed in recent years to separate them. About one in five Standard & Poor's 500 companies separate the jobs.
Supporters argue that an independent chairman can provide a check on the CEO's power. Shareholders also frequently push for separation at turbulent times for a company.
In JPMorgan's case, the move to separate the jobs was put on the ballot before the $2 billion loss was unearthed. It was also on the ballot last year, but it received far less support then, 12 percent.
JPMorgan stock climbed throughout the morning and was up 3 percent by midday, on a day when the broader stock market was up only slightly. Investors pummeled JPMorgan stock in the first two trading days after the loss was revealed, driving it down 12 percent and wiping out almost $20 billion in market value.
Dimon said he did not expect the trading loss to jeopardize JPMorgan's quarterly stock dividend, which is 30 cents per share.