One of Moretti's main thesis is that there has been a "Great Divergence" on-going since the 1980s. Moretti sums his idea as-so:
America’s new economic map shows growing differences, not just between people but between communities. A handful of cities with the “right” industries and a solid base of human capital keep attracting good employers and offering high wages, while those at the other extreme, cities with the “wrong” industries and a limited human capital base, are stuck with dead-end jobs and low average wages. This divide—I will call it the Great Divergence—has its origins in the 1980s, when American cities started to be increasingly defined by their residents’ levels of education. Cities with many college-educated workers started attracting even more, and cities with a less educated workforce started losing ground. While in 1969 Visalia did have a small professional middle class, today its residents, especially those who moved there recently, are overwhelmingly unskilled. Menlo Park had many low-income families in 1969, but today most of its new residents have a college degree or a master’s degree and a middle- to upper-class income. Geographically, American workers are increasingly sorting along educational lines. At the same time that American communities are desegregating racially, they are becoming more segregated in terms of schooling and earnings.
Regions of boom and bust are nothing new in economic geography, but never before has education played such an important role. Communities themselves are specializing immensely on skilled, education-needing industries.
Moretti discusses his idea and the new geography of jobs in America in his lengthy Salon article. There are counterweights to this education rise, service industries and technical jobs (carpenters, plumbers, etc) will always complement any strong professional population. Meanwhile, one also has to consider the potential upcoming higher education bubble and the inflation of degrees being awarded.