But the divergence is more than just between workers who benefit from globalization and those that don’t. It’s also between the places those two groups tend to live. That’s because of something that economists refer to as the agglomeration economy. Basically, it means that companies want to locate near other innovative companies so that they can find skilled and specialized workers, which in turn makes those companies even more productive. They want to be places where the job market is full of educated workers who they can hire. They want to be near the specialized services, like venture capitalists or bankers, who can help make their companies even better or provide funding. And they want to benefit from what Moretti calls a “knowledge spillover,” in which people at certain types of companies learn from innovations created at other companies near them, through professional and social networks.

This concentration of good jobs in a few hubs creates more opportunity for everyone, not just people with college degrees. Innovation workers can command higher salaries than people in other industries such as manufacturing do. With their money they eat out more, go shopping, spend on entertainment, and pay for services like dry cleaning, house cleaning, and childcare. All of this spending creates more jobs. Moretti has analyzed 11 million workers in 320 metropolitan areas, and found that every new high-tech job in a metropolitan area creates five additional local jobs. Every new manufacturing job creates just 1.6 additional local jobs. “A city that has a lot of college grads also tends to have a different economic ecosystem,” Moretti told me. Yet such cities are cost prohibitive for many of the lower-skilled people who might want to locate there. In Indianapolis, for instance, housing prices have surged as more people have moved there, pricing many families out. Moving to booming cities is both a solution for low-skilled people, then, and an impossibility.