Answer:
the college wage premium
Step-by-step explanation:
The college wage premium is the difference between the average earnings those earned by individuals with a college degree but is not a graduate and the one who did not attend college and do not have a college degree.
In the context, Don and Cal are both friends. After their school, Don joined to work in an organization while Cal attended university and earned a college degree and then he joined an insurance company. Don earned 40,000 dollar in a year in his 10 years of work while Cal earned 70,000 dollar in one year after working for 5 years. This difference is due o the college wage premium which states that a college graduate degree would earn you more wage than a non graduate degree.