Sorenstam's lead over Ochoa slipped by just .21 average points as the Swede finished second behind Ochoa at Bighorn.
The next four places remained unchanged as Karrie Webb, Cristie Kerr, Juli Inkster and Paula Creamer remained third through sixth.
Ai Miyazato and Jeong Jang exchanged places with Miyazato up to seventh and Jang down to eighth. Shiho Ohyama and Michelle Wie rounded out the top 10 again this week.
There was not much change from 11-20. Pat Hurst held steady in 11th and was followed by Mi Hyun Kim, Yuri Fudoh, Se Ri Pak, Hee-won Han and Seon-Hwa Lee.
Sophie Gustafson took third behind Ochoa and Sorenstam. That helped her climb two notches to 17th. Jee Young Lee remained 18th, while Natalie Gulbis fell two places to 19th. Morgan Pressel held on to the 20th spot again this week.