NAUCALPAN DE JUAREZ (Mexico) • Golfers build their professional careers on the conceit that they are better than everyone else. But, since 1986, only 20 men have been able to say that they are No. 1.

The official world golf rankings were conceived as a promotional vehicle and have grown to become - what, exactly?

The sixth-longest reign at the No. 1 spot belongs to Luke Donald, who has never won a Major.

Phil Mickelson has five Major victories but has never been the world No. 1.

The ranking, for so long prefixed to Tiger Woods' name like a royal title, has become much more democratic in recent years.

From 1999 to 2010, he twice spent five-year reigns at No. 1.

Since Rory McIlroy rose to No. 1 for the first time five years ago, the top ranking has exchanged hands 19 times among seven players, including Woods.

"I think for a lot of guys, it's an ego thing," said the Ulsterman, who is lurking at No. 3.

He can knock off Dustin Johnson if he wins the World Golf Championships event (this morning, Singapore time) at Club de Golf Chapultepec in Mexico City and Johnson finishes outside the top four.

McIlroy carded a one-under 70 in the third round for a 10-under 203 total and was two strokes behind leader Justin Thomas (66) of the USA and one adrift of Johnson (66).

"It's just nice to be able to say that you're the best in the world at what you do," McIlroy said.

American Johnson was asked last week if he agreed with McIlroy that the No. 1 ranking was mainly a boost to the ego.

"Yeah, I mean, I guess," he said.

For the American, the world No. 1 ranking is akin to the Grammy Lifetime Achievement Award or the Honorary Award at the Oscars. It is earned for one's body of work.

For that reason, he considers it a taller mountain to scale than a victory in one of the Majors.

"You've got to play very well for a long period of time," said the reigning US Open champion.

"Winning a Major is unbelievably difficult, too, but you only have to play well for four days."

The world-ranking points for each player are accumulated over a two-year rolling period, with an emphasis on recent performances.

Johnson, 32, won the Genesis Open in Los Angeles last month to overtake Jason Day, who had been No. 1 for a total of 51 weeks.

World No. 4 Hideki Matsuyama, who has yet to win a Major, also had a chance to supplant the Australian with a victory in Los Angeles, but he missed the cut.

He said that the top ranking was not a focal point and that he was not stressing about it, but to become No. 1 would be historic for him.

The 25-year-old would become the first player from Japan to reach the men's summit, much as McIlroy was the first to plant Northern Ireland's flag at the top.

NYTIMES