Between 1982 and 2000, California built twenty-three new prisons and, Gilmore found, increased the state’s prison population by 500 percent. [...] Gilmore outlines four categories of “surplus” to explain the prison-building boom. There was “surplus land,” because farmers didn’t have enough water to irrigate crops, and economic stagnation meant the land was no longer as valuable. As the California government faced lean years, it was left with what she calls “surplus state capacity”—government agencies that had lost their political mandate to use funding and expertise for social-welfare benefits (like schools, housing, and hospitals). In the wake of this austerity, investors specializing in public finance found themselves with no market for projects like schools and housing and instead used this “surplus capital” to make a market in prison bonds. And finally, there was “surplus labor,” resulting from a population of people who, whether from deindustrialized urban centers or languishing rural areas, had been excluded from the economy—in other words, the people from which prison populations nationwide are drawn.