Ko, the 16-year-old wunderkind from New Zealand, suggested recently that she may turn professional in time for next year's New Zealand Open. She's won three professional tournaments as an amateur, including the last two CN Canadian Women's Open on the LPGA Tour.
She and Ryu, from South Korea, each improve their rankings one spot this week as the rankings adjust points assigned from older tournament results. Choi So-yeon drops two spots, allowing for Ko and Ryu to move up.
The same situation occurred lower in the Top 10, with Feng Shanshan falling two spots to 10th and I.K. Kim and Catriona Matthew each up one place to eighth and ninth, respectively.
Further changes are possible as Ko and Ryu, in a statistical tie, are just 0.03 points in average ahead of Choi and Matthew and Feng, also rounded to the same average, 0.06 points back of Kim.
Inbee Park enters her 24th week as the No. 1-ranked women's golfer.
The LPGA is off against this week before beginning an Asian swing Oct. 3-6 with the Reignwood LPGA Classic in Beijing.
The world women's golf Top 10, listing player's name, home country and ranking points average:
1. Inbee Park, South Korea, 12.56
2. Suzann Pettersen, Norway, 10.61
3. Stacy Lewis, United States, 9.72
4. Lydia Ko, New Zealand, 7.35
5. Ryu So-yeon, South Korea, 7.35
6. Choi Na-yeon, South Korea, 7.32
7. Karrie Webb. Australia, 6.02
8. .I.K. Kim, South Korea, 5.57
9. Catriona Matthew, Scotland, 5.51
10. Feng Shanshan, China, 5.51
Beyonce flaunts bikini body, Blue Ivy in vacation pics
Kate Middleton recycles dress at movie premiere