No matter how you slice the data, the major reason two-thirds of workers with college degrees making more than $50,000 a year change jobs is for a significant increase in pay. That's what a recent annual workforce study by New York-based executive recruiting firm, F-O-R-T-U-N-E Personnel Consultants found. That finding held true regardless of gender or age. And, in what suggests even more scrambling in the future for competent workers, only 4.8% of those surveyed said that they did not expect to change jobs over the next 10 years. Companies looking to keep their best workers should keep in mind the top two reasons workers said that they stay with their current employers: challenging work, 25%; and the ability to balance work and family, 24.2%. Two significant gender differences: The opportunity for career advancement was twice as important to men than to women, and the work environment and corporate culture was twice as important to women than to men.