Population density, in its simplest form, is 'total population in a given region' divided by the 'area of the given region' - thus for deserts the population density will be very low, and for some urban centres it will be very high. However, the population density can suffer from the same problems as all statistical methods: an obvious example is that some areas of many cities are likely to have a very high population density during the day, but a very low one at night.