Jamie Dimon, chair of JPMorgan Chase, said he was ‘far more worried than others’ about serious market correction Jamie Dimon, chair of JPMorgan Chase, said he was ‘far more worried than others’ about serious market correction The chances of the US stock market crashing is far greater than many financiers believe, the head of America’s largest bank has said. Jamie Dimon, who is the chair and chief executive of the giant Wall Street bank JPMorgan Chase, said he was “far more worried than others”