Hierarchy

• Universities typically hire and pay their faculty according to a system of ranks. Instructors stand at the bottom of the hierarchy, followed by assistant professors, associate professors and professors at the top. According to the Bureau of Labor Statistics, in the 2008-2009 school year, "the average [salary] was $108,749 for professors, $76,147 for associate professors, $63,827 for assistant professors, [and] $45,977 for instructors."
  
  

Two-Year vs. Four-Year

• Faculty at four-year institutions typically make more than instructors at two-year institutions. A CNN article says there is a 50 percent difference in pay between community college professors and university faculty. According to a survey of human resources professionals at universities, the average salary at community colleges was $51,000 in 2008.
  
  

Tenure and Part-Time

• Universities protect academic freedom by granting professors tenure, under which they cannot be fired or silenced except in cases of extreme misconduct. Obtaining tenure typically takes about seven years. The rank of assistant professor is the first step among tenure-track professionals. Many universities are shrinking the number of tenure-track positions in favor of part-time instructors who are more flexible, less expensive and typically don't require health benefits.
  
  

Other Income and Benefits

• Because of their expertise in their field, many professors earn extra money by serving as consultants or expert witnesses, where appropriate. In addition to health benefits, instructors also have unique benefits not granted to many workers, including free or reduced tuition for dependents, access to campus facilities such as labs, gymnasiums and meeting rooms, travel allowance and paid sabbaticals, according to the Bureau of Labor Statistics.