The win was Harrington's first and only in 2001 despite seven-runner up finishes on the European Tour.
Tiger Woods remained comfortably in first as he returns to competitive golf this week. He will team with David Duval, ranked third this week, as the duo tries to successfully defend their title at the World Golf Championships - EMC World Cup in Japan. Phil Mickelson held on to his second-ranked spot.
Ernie Els came in fourth this week, followed by Davis Love III, Sergio Garcia, PGA champion David Toms and Vijay Singh, each of whom held their positions from last week.
Darren Clarke finished third on the Order of Merit in 2001 and moved up one notch to No. 9. Harrington rounded out the top-10 as his victory at the Volvo Masters moved him ahead of Clarke on the European Tour's money list.
Mike Weir, winner of the Tour Championship last week, dipped two places to 11. Retief Goosen, the 2001 U.S. Open champion and European Order of Merit winner, fell one spot to 12, as did seven-time Order of Merit champion Colin Montgomerie, who dropped to 13th this week.
Bernhard Langer and Jim Furyk, Ryder Cup players on opposite sides, stayed 14th and 15th, respectively.
Scott Verplank, a wildcard Ryder Cup selection for the United States, dropped three spots to No. 16. He was followed by a trio of two-time PGA Tour winners from 2001 -- Jose Coceres, Bob Estes and Scott Hoch.
Chris DiMarco fell one spot to round out the top-20.
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