Rory McIlroy signs off on a majestic performance. Photo Eoin Clarke/www.golffile.ieBigger doesn’t always mean better, especially for the statistics freaks of the sports world.

Rory McIlroy’s phonomenal eight-stroke win at Kiawah Island’s Ocean Course beat the previous margin of victory record for the US PGA, set by Jack Nicklaus at Oak Hill in 1980, by a shot. But was it the best?

Using the Z-score system, Grantland.com’s Bill Barnwell (thanks to reader Kevin for the link) has done a statistical analysis of the win and while it goes down as the best of McIlroy’s career, overtaking last year’s eight-shot win in the US Open at Congressional Country Club, it ranks only third in the list of all time PGA wins (since 1960) behind Davis Love’s 1997 win at Winged Foot and Nicklaus’ victory of 1980.

Barnwell explains:

As it turns out, it was. McIlroy’s score of 275, weighed against the rest of the field, produced a Z-score of -3.15. He finished just under 15 strokes ahead of the average golfer who finished four rounds, and while he won by eight strokes, there were two dozen players within four shots of second. By a fraction of a stroke, it narrowly topped McIlroy’s U.S. Open performance from last year to become the best performance of McIlroy’s career.

Was it the best PGA Championship performance of the modern era? Nope. In fact, while McIlroy’s performance topped Nicklaus’s record, Nicklaus’s run in 1980 represents one of the two scores that topped what Rory did this weekend. The best performance at a PGA Championship since 1960 belongs to Davis Love III, who was transcendent at Winged Foot in winning the 1997 championship. Love “only” won by five strokes, but consider that his 11-under-par mark made him one of just five players in the entire tournament to finish at par or better. To produce a score that topped Love’s, McIlroy would have needed to chop three strokes off of his score and shoot a 272, which would have resulted in a Z-score of -3.60. That gives the world’s best golfer some homework to do for the next 25 years of his career.

It’s interesting to note that Love won the 1997 US PGA using a wooden headed driver, making him the last player to win a major using persimmon. According to Jaime Diaz’s Sports Illustrated story on Love’s lone major victory to date, the current US Ryder Cup captain “averaged 307 yards off the tee to lead the field in driving distance. (Tiger Woods at 298 yards and John Daly at 296 were the next longest.)”

[Has anyone got Rory’s driving average last week to hand?]

Tiger Woods’ 15-stroke US Open win at Pebble Beach in 2000 ranks as the greatest major win since 1960 with a Z-score of -4.12 with Love’s 1997 US PGA in second place.

Padraig Harrington’s four-shot win in the 2008 Open Championship Royal Birkdale ranked 15th ahead of McIlroy’s 17th ranked US Open (-3.09 vs -3.07).

He might be third to Love and Nicklaus in the US PGA stakes, but McIlroy now takes over as the most impressive Irish major winner ever. Not bad.