If One Looks at U

If one looks at U.S. Census data and finds that the average white salary is $39,000 while the average black salary is $36,000, which of the following is not likely to be a significant cause of this difference given U.S. labor market demographics?

A) Whites are more inclined than blacks to work part-time.
B) Blacks have less education than whites.
C) Labor market discrimination.
D) Whites are more likely than blacks to hold positions in upper management.
E) Whites are more likely than blacks to own their own business.