People who get higher pay are more willing to relocate—especially to undesirable locations at the company's behest... A corporate secretary may change companies in the same town; a corporate executive is more likely to change towns with the same company. A talented corporate secretary sees an invitation to relocate as an invitation; a future corporate executive sees an invitation to relocate as an opportunity—and an obligation.

p. 93-94. - Why Men Earn More (2005)