WASHINGTON (AP) — For years, many Americans followed a simple career path: Land an entry-level job. Accept a modest wage. Gain skills. Leave eventually for a better-paying job.

The workers benefited, and so did lower-wage retailers such as Wal-Mart: When its staffers left for better-paying jobs, they could spend more at its stores. And the U.S. economy gained, too, because more consumer spending fueled growth.