Urbanization is the societal trend where the proportion of people living in cities increases while the proportion of people living in the country side diminishes. Urban refers to the geographic territory within or close to a city. The governments of the world define urban in different ways, but it is safe to assume that between 2-5,000 inhabitants in a city is the minimum required to call a geographic territory urban. Some urban areas such as Tokyo, New York, Mexico City, Shanghai, and Lima range from 35 million down to 7 million people living in those cities (see www.PRB.org Retrieved 13 April, 2009 from "Most Populous Urban Agglomerations 2005.")
A few factors have to be in place in order for urban growth to occur. These theoretical approaches help in understanding urban development. Agricultural Surplus Theory claims that as farming skills increased, a surplus of basic foodstuffs existed. The surplus freed certain people from having to produce their own food and let them develop other occupations. Central Place Theory claims that farmers needed a central place to trade or sell their surplus and cities developed in those central places. Trading Theory claims that the surplus was not as important as were the specialists who knew how to create it and do other occupations. There must also be a transportation route (river, trail, valley, railroads, harbors, or oceans). Once settlers move in, the city will flourish or fail depending on its ability to continue to draw in people seeking opportunities.
Rural refers to the geographic territory in the less populated regions of a society. Mona, Utah; Hell, Michigan, and North Pole, Alaska are just a few of the less populated rural areas in the US. If you grew up in the United States you can find out all types of recent information about your home town (rural or urban) by going to http://www.census.gov/ and typing in the "Population Finder" section of the homepage. I typed in the zip code for Hell, Michigan (Zip code 48619) and it brought up a table of all the 481Ézip code areas and some interesting information on these cities. According to the 2000 US Census, Hell had 19,840 inhabitants and 59.89 miles of land area or 331.3 people per square mile. I also typed in New York City, New York. It indicated that in 2007 there were about 8,274,527 people living there. It also indicated that some of the city has no residents while in its most densely populated areas it has over 200,000 people per square mile living there (see TM-P002, Persons per Square Mile: 2000 NY, NY).
Sociologists who study the cities often use this simple concept called Population Density=the number of people per square mile or square kilometer. The Population Reference Bureau is free online at www.PRB.org ). It provides details about every country of the world including the US. See Table 1 below for some 2000 population density estimates which show the variety of densities worldwide.
Table 1. Population Densities for Select Countries and Regions*
United States 74
More Developed 60
Less Developed 153
Latin America 65
Western Europe 429
Eastern Europe 42
*All values converted to people/square mile. Retrieved 13 April 2009 from http://www.prb.org/Educators/TeachersGuides/HumanPopulation/Migration/QuestionAnswer.aspx original retrieved from World Population data Sheet, 2000.