Economists of education think much of the purported value of a college degree comes not from what college study adds to the value of a job-seeker, but from what a college degree signals about characteristics the job-seeker had to have to be admitted to college. One thing a college degree signals is a THRESHOLD level of scholastic ability (the better term for what IQ scores estimate). In the United States, there are severe legal difficulties related to using mental test scores to screen job applicants--the same difficulties don't relate to requiring all job applicants to have a college degree.
