Consider this quote from an article in the wall street journal: "the stock of educated workers isn't increasing fast enough to keep up with rising employers are paying the typical four-year college graduate [without graduate school] 75% more than they pay high-school grads. twenty-five years ago, they were paying 40% more. employers insist on ever better-educated, skilled workers. " source: david wessel, "lack of well-educated workers has lots of roots, no quick fix," wall street journal, april 19, 2007, page a2. which of the following best explains the rapid increase in the wage differential between college graduates and high school graduates?