In the 1970s, there was an oversupply of college graduates, which reduced the average annual income of college graduates to a level that is only 18% higher than that of workers holding only high school diplomas. By the 1980s, college graduates The average annual income is 43% higher than that of workers who only hold a high school diploma, although the supply of college graduates has not declined in the 1970s to the late 1980s. Which of the following, if correct in the late 1980s, best reconciled the obvious differences above? ['The economy has slowed, reducing demand for college students.', 'The quality of high school education has improved.', 'More high schools offer them career guidance programs than in the 1970s.', 'For the first time in 20 years, an oversupply of job seekers with only a high school diploma.']