Critical Reasoning

In the 1970’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 1980’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 1970’s and the late 1980’s the supply of college graduates did not decrease.
Which of the following, if true, in the late 1980’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 1970’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.

D?

IMO E

1970 oversupply of college grads --> salary of college grads goes down -->income diff between gollege grad and high schoold diploma goes down

late 1980 oeversupply of high school diploma --> salary of highschool diploma goes down --> income diff between gollege grad and high schoold diploma goes up

yeah, i too had to choose between D and E, I guess D assumes too much afterall...

My pick E.

Same reasoning as Durgesh's

The number of people available in a particular category increases and there are more people willing to work in that category. Employers can cherry pick whom they want and the increased competition drives down wages. Even if the Graduates pay remained same, the other category might have fallen so much that the difference is now 43%

OA is E.

I picked D though.

E) There was for the first time in 20 years an oversupply of job seekers with only high school diplomas.....

wat confused me in E was the part "first time in 20 years" as though the 43% difference was seen only in one particular year.

Can anyone elaborate the thought process behind E, specially refering to the bold part.

Thanks

Actually this bold part makes Option D very strong ....

it tells that this oversupply of highschool diploma dint happen in 1970 .... so the salaries of highschool diploma guys were good (relatively)

May be the purpose of this bold part is just to trap .... someone might think that there is no reference of "20 years" in the question so this option is out of scope.....

Looking at it now, E makes sense