There are now something like 1000 cities with over a million population. Urbanization has occurred with astonishing speed in the past 30 years, and around the world the majority of that growth has been in the form of urban slums. This growth has been driven by a number of factors, including overall population growth, forced relocations, IMF and World Bank policies that have driven peasants off their land, refugee flight, and so on. The old, pre-1970, drivers of urban growth have largely disappeared. People no longer move from the countryside to major cities in order to find good employment: good employment is simply not to be had in many countries. The new migration is a response to desperate or impossible circumstances.
So now we are faced with a situation in which over 1 billion potential workers are without steady, or any, employment. They make do, if at all, only through a shadow economy including street peddling, sporadic and inefficient menial labor, and criminal activity.
Cities provide little or no services to the new slums, the peri-urban slums of the 21st century. Infrastructure is non-existent, so disease is rampant.
Davis offers no solutions. The situation seems hopeless, frankly, because the depth of poverty, and the variety of ways that people have found with coping with it, itself causes divisions among the poor that prevent them from taking effective collective action on their own behalf. And certainly there is no prospect that the elites or middle-class will see deeply enough into their own eventual self-interest to take effective steps to end this situation, or even to ameliorate the worst of it.