World: Stuart Elliott in America.

New York is the town where, the song goes, if you can make it there, you'll make it anywhere. Perhaps that's the strategy behind a sudden spate of shifts at the top of major agencies in the Big Apple.

Bartle Bogle Hegarty, Lowe & Partners Worldwide, Saatchi & Saatchi and TBWA\Worldwide all have new chief executives, presidents or general managers for, or in, New York. (In a couple of cases, there are new chief creative officers or executive creative directors, too.)

And some of those changes are triggering rejigs at other agencies, including Arnold Worldwide and McCann Erickson Worldwide, as they seek to replace - or cover for, at least for the time being - New York management that left for elsewhere.

The latest round of musical chairs comes not long after new faces arrived in the New York outposts of agencies such as Foote Cone & Belding, Publicis Worldwide and J. Walter Thompson. So what is it, something in the water?

Which, contrary to stereotype, is actually better in New York than in many other American cities. (It's just that with so many other options from which to choose at the city's fabled nightspots, who's drinking water?)

A glance at the calendar can offer reasons for some of the switches.

Summer, traditionally a time of torpor on Madison Avenue, is over and autumn has arrived with its need to gear up for the crucial fourth quarter of the year, typically a make-or-break period for many clients.