LONDON — The sudden announcement on Wednesday that Alex Ferguson will retire in two weeks’ time after almost 27 years as manager of Manchester United has shaken its shares on the New York Stock Exchange, to say nothing of its effect around the sporting world.

The club’s share price fell as much as 3.5 percent in early trading in New York within hours of the statement from Britain though it recovered some and was down 1.44 percent in afternoon trading. The decline reflects how much of a business sports has become, and how much Ferguson has meant to United’s dominant position in the global game.

‘'It is the right time,'’ he said Wednesday in Manchester.

At 71, he faces a hip operation in the coming weeks, and he has served his time with a club where he has built, and ruthlessly rebuilt, the playing squad five times to sustain its leading position atop the English Premier League and remain competitive in Europe.

But it is beyond the playing field where the club has grown. Forbes magazine rates United and the Spanish giant Real Madrid as the two clubs whose $3 billion valuation makes them by far the greatest sporting franchises in the world.