Sari Baldauf did itat Nokia, Brenda Barnes at PepsiCo and Penny Hughes at Coca-Cola. All three women quit top jobs at the height of their careers to pursue outside interests and responsibilities.

They are the headline-grabbing tip of an iceberg. Women graduates enter many companies and professional firms in nearly equal numbers to men, but they drop out as they rise up the ranks. How to hold on to this talent, and increase women's representation in senior jobs, has become a serious concern.