Ha Na Yang (twice) and Hyo Joo Kim have helped deliver this year's Korean dominance which has only been split by Haru Nomura from Japan and the USA's Lexi Thompson.
This week's event at the Aviara Golf Club has 98 of last year's top 100 money earners teeing it up as they sharpen their games for the first major. The experienced Christie Kerr will defend the title she won with a record score last year.
Much of the focus has been on Jang with two wins so far and a worst finish of 13th in the six tournaments she has played this year.
However they will all be eying Ko who may not have won a tournament but has kept her form and a scoring average well below 70.
She tied for third at the Coastes Championship, second at the Australian Open, tied 15th at the HSBC champions and second last week at the JTBC Founders Cup.