"Almost one billion people today live in conditions that UN-Habitat classifies as slum households, out of approximately 3.9 billion people who live in cities. If the UN's estimates are accurate, approximately 2.5 billion more people will be living in cities by 2050--and not in perfect shining skyscrapers set in pastoral landscapes. Instead, over two thirds of this new urban population, some two billion people, are projected to fall under UN-Habitat's category of slum households, deprived of at least one of five basic living conditions. Many of what UN-Habitat considers slum households are part of self-built neighbourhoods, the result of informal occupation and construction. If two-thirds of our new urbanization will largely be the result of people building their own homes and neighborhoods outside of formal planning and processes, and with close to a billion people living in such situations already, this is not a fringe phenomenon. It is part of the mainstream, and it is on its way to becoming the majority of future urbanization--and thus the title for this collection: Metropolis nonformal."--Page 9.