How many management consultants does it take to change a lightbulb? Nobody knows – they never get past the feasibility study. Nonetheless, former McKinseyites dot the corporate landscape. There are 150 alumni globally running companies which each boast more than $1bn in revenues, including Standard Chartered, Lego, Starwood Hotels and BHP Billiton. The latest mega-company to be run by a former McKinsey man is Morgan Stanley, where James Gorman becomes chief executive in January.

Compliments for Mr Gorman include some classic consultant attributes. He is “cerebral”, which may just mean bright. He is also apparently a “brilliant strategic thinker”. Yet similar sentiments were expressed about former Morgan Stanley chief executive Philip Purcell, also an ex-McKinsey partner, who was unceremoniously ousted in 2005 having singularly failed to win over the rank and file to his vision for the bank. Rather, success at the top depends less on an analytical mind than the X-factor of compelling leadership. But even that does not always work. Shares in Unicredit, Europe's 7th biggest bank and staffed by ex-McKinseyites, have performed no better than its peers this decade.

consultant's background may, however, bring with it certain advantages. For example, Mr Gorman is said to feel comfortable surrounded by strong, talented executives, who provide specialist knowledge he lacks. (Consultants, after all, often simply bring an outsider's objective eye to a business rather than new information.) If that is the case, he will be unusual on Wall Street, where paranoid egos often prefer a paucity of competing talent. The crisis has further thinned the depth of Wall Street's management pool. Morgan Stanley's board had a limited number of internal names, and yet interviewed no external candidates. Wall Street needs to change more than its lightbulbs, and should welcome all hands in the effort to do so.