Why do people quit their jobs? Often its because they just dont fit into the job they were hired to do. Thats what nearly 40% of employees interviewed in exit surveys told employers in a recent nationwide survey conducted by Princeton, N.J.-based Caliper, a global psychological testing and human resource consulting firm. Another 26% cited a better-paying job as the reason for their job switch. But the fact that the greatest percentage quit because the job didnt match their expectations -- that is, not challenging enough, or with slim potential for advancement, or no decision-making ability -- means that employers should think twice before filling empty positions "with anyone who seems even remotely appropriate," says Herbert M. Greenberg, president and CEO of Caliper. "This short-term solution rarely works because as soon as new employees realize their jobs dont fit, they become disgruntled and start looking elsewhere. [That] leaves the company with the same empty seat, as well as a deepening negative impact on the entire organization."