Birth and Death Rates—The annual number of births and deaths per 1,000 in the total population. These rates are often referred to as “crude rates” since they do not take into account a population’s age structure. Thus, crude death rates in more developed countries, with a relatively large proportion of older individuals, are often higher than those in less developed countries.

Demography—The scientific study of human populations, including their size, composition, distribution, density, growth, and other demographic and socioeconomic characteristics, and the cause and consequences of changes in these factors.
 

Megalopolis—A heavily populated region which embraces one or more large cities.

Demographic Projections—Estimates of demographic statistics and trends (for example, future population size). Values given in data tables are based on a recent census, official national data, or UN, U.S. Census Bureau, or World Bank projections. The effects of refugee movements, large numbers of foreign workers, and population shifts due to contemporary political events are taken into account to the extent possible. Such events can introduce a high degree of uncertainty into the estimates.

Total Fertility Rate—The average number of children a woman will have assuming that current age-specific birth rates will remain constant throughout her childbearing years (usually considered to be ages 15-49).

Rural-Urban Migration—Relocation of individuals from the countryside to cities, a common demographic trend, particularly in developing nations.

Trans-National Migration—Relocation of individuals across national boundaries. Emigration of Mexican citizens to the United States is an example.