The Three Basic Demographic Variables Fertility, Mortality and Migration Essay Example

The history of world migration can be divided into three overlapping periods: free individual migration, group migration, and restricted migration.

The predominant motive behind free individual migration is economic need and the desire to improve one’s lot. Historically, group migration is usually caused by invasion, conquest, displacement, forced labor or slavery, and colonization. In modern times, small group migration (families and group of professionals) increased due to “the opening up of the world by faster and more reliable transport facilities and the improved knowledge of other countries and continents made possible by new communication media. ” (Thomlinson, 1976, p. 85)

The most popular wave of small group migration since the time of Ancient Greece is known as the “Brain Drain”. The brain drain “pulls people from developing countries to developed ones, and from moderate-salaried nations to high-paying ones. ” (Thomlinson, 1976, p. 289) In the twentieth century, rules that control migration (such as setting up of quotas and restriction) and the prohibition of all movement of certain types of people (criminals and those suspected to be terrorists and communists), severely curtail migration, particularly in the United States of America.

The most fundamental equation in demography is: Final Population = Initial Population + Births — Deaths + In-migrants — Out-migrants. Due to the ever-changing factors that affect the three demographic variables previously discussed, it is therefore concluded that population analysis and demographic studies “require research methods that permit the calculation of accurate rates of births, deaths, and in- and out-migration. ”