In the 1970â€™s there was an oversupply of college graduates. The oversupply caused the average annual income of college graduates to fall to a level only 18 percent greater than that of workers with only high school diplomas. By the late 1980â€™s the average annual income of college graduates was 43 percent higher than that of workers with only high school diplomas, even though between the 1970â€™s and the late 1980â€™s the supply of college graduates did not decrease.
Which of the following, if true, in the late 1980â€™s, best reconciles the apparent discrepancy described above?
(A) The economy slowed, thus creating a decreased demand for college graduates.
(B) The quality of high school education improved.
(C) Compared to the 1970â€™s, a greater number of high schools offered vocational guidance programs for their students.
(D) The proportion of the population with at least a college-level education increased.
(E) There was for the first time in 20 years an oversupply of job seekers with only high school diplomas.