From Homeland, which was published in September by Crown.

In his 2005 book Planet of Slums, Mike Davis pointed out that, since the Seventies, the world’s poor countries have urbanized at a rate that puts Europe’s nineteenth-century urbanization to shame. But whereas those European experiences of urbanization were part of an industrial revolution that saw growth accelerate dramatically, the more recent urbanization of what used to be called the Third World has occurred in places where economic growth is either low, slowing down, or nonexistent. Megacities have grown so much not because they are hotbeds of economic opportunity but because the best way for people to survive when they cannot find secure, salaried labor is to live near as many other people as possible.

The term for the people who live in this global archipelago of slums is “surplus population.” They are surplus with respect to the economic system they inhabit; the economy has no need for their labor and is unable to grow at a rate that would provide them with formal employment. They rely instead on domestic labor, scavenging, and temporary construction work paid in cash. In 2018, more than 60 percent of the world’s workers earned their livelihoods primarily through informal work. Because these people are not technically unemployed, this surge in informal work is not reflected in standard economic data. But it defines the gap separating the world’s rich countries from its poor ones.

In this light, the economic rationale behind America’s war on terror becomes clear. The country faced a series of problems stemming from the authoritarian rule, urban poverty, and social instability that plagued the countries where growth had failed. The United States believed that the problems facing these states could be kept more or less at arm’s length until September 11; for the American ruling class, it revealed that belief as illusory. America would need to confront these problems more directly, with a decentralized military effort. That’s where the expanded war on terror came from. It might not solve the problems facing a low-growth world, but it could at least insulate the United States from the effects. The war on terror is a tool for managing the very surplus populations that the end of American-led economic prosperity helped to create—people whom the United States now finds itself unable and unwilling to help.