American Lindsay Davenport will finish the season as the world number one for the fourth time in her career.
After world number two Kim Clijsters of Belgium was knocked out at the round-robin stage at the WTA Championships on Thursday, Davenport was again assured of the year-end top spot.
She has achieved the feat for the last two years despite failing to win a Grand Slam tournament, mirroring the situation in 2001.
She also ended as world number one in 1998, the year she won the U.S. Open.
Three times a Grand Slam winner in all, Davenport has captured 51 titles, six of them coming in 2005.
On Thursday, she fell to defending champion Maria Sharapova 6-3, 5-7, 6-4, but because she had already won two matches in her group qualified for the semi-finals along with Sharapova, Amelie Mauresmo and Mary Pierce.
