Institutional shareholders generally hailed the New York Stock Exchange's merger with Archipelago as a momentous change that would reduce trading costs for investors.

Harold Bradley, a chief investment officer at American Century, which owns a stake in Archipelago and executes 50-70 per cent of its trades electronically, praised John Thain, NYSE chief executive, for a "brilliant" move. By emulating European exchanges' move to electronic platforms, the NYSE would push ahead of its rivals and prepare it for further expansion. "The whole world should be afraid," said Mr Bradley, whose employer manages $78bn.