The 1990s witnessed one of the longest economic expansions in the history of the United States. According to Dean Baker of the Center for Economic Policy and Research,

The period from the fourth quarter of 1995 to the end of 2000 was the economy’s best sustained economic performance since 1973. . . . Annual productivity growth in this period averaged almost 2.5 percent. This is more than a half percentage point above the rate of productivity growth in the seventies and nearly twice the growth in the eighties. . . . Real wage growth also picked up during this period, with average hourly compensation rising at a real rate of 2.2 percent annually. . . . In addition, the unemployment rate sunk to its lowest point in thirty years, bottoming out at 3.9 percent for several months in 2000.

In the wake of this growth, a remarkable new theory emerged—that the...