ABSTRACT
The world's population may fall to just a billion, and the most pessimistic doomsters–who see agriculture as a multimillennium failed experiment–caution that the world could be down to tens of millions. The subsequent 100 years of development, during the 20th and early 21st centuries, involved tremendous population growth within and extension of the urban areas, including the emergence of the megapolitan Sun Belt in the South and West. As a nation, voters shape the public policy that can alter the course of how many people live in the United States and where they will live. For example, a dramatic shift in public opinion can produce a new politics of immigration. Most turn-of-the-20th-century estimates had the nation at 300 million by the middle of the 20th century, whereas that number was reached only in 2006. Early in 20th century, there was a considerable social distance between Eastern and Southern Europeans and Americans descended from northwestern European immigrants who had arrived earlier.
