Two of the biggest names in Wall Street research are leaving Merrill Lynch in another sign that Bank of America's acquisition of the bank has spurred many long-time employees to rethink their commitment to the organisation.

David Rosenberg, Merrill's chief North American economist, will leave in May and return to his native Toronto, where he will join a buy-side firm, Gluskin Sheff & Associates, said a person familiar with the matter.