ABSTRACT
Large cities are virtually mini states; if the ranking of the most populous cities were to be superimposed on the, Mexico City would rank 64th, ahead of the majority of the countries of the world. Like countries, cities grow at differing rates. However, larger cities generally tend to grow at slower rates than the smaller ones, because the former have already population levels. Following this trend reached sizable population levels. The average population density at the national level is 400, but level it is over 40,000 per is about 400, but at the urban level it is over 40,000 per square mile. The growth in density takes place in most cases without any corresponding increase in the physical size of cities. Whereas US cities generally are physically larger, many Asian cities are much smaller. The historically have been compact physical units. The average size of European cities is about 50 square miles.
