This document discusses reasons for wage differentials between similar jobs and workers. It explores factors like education, skills, experience, job characteristics, firm size, geographic location, and discrimination that can influence wages. Specific data is presented on average wages by occupation from 2007, highest paid CEOs in 2005, and hourly earnings by occupational group from 2006 to illustrate wage differences. Human capital theory is discussed as well as compensating differentials, prospects for wage growth, and costs of job search, monitoring and mobility.