Push factors are factors that encourage people to leave a region or country. These can vary from economic factors to daily lifestyle changes. 

The USA has promising economic and educational pull factors. Many immigrants to the USA come to the country in hopes of starting a new life that is better financially than their last one. Pull factors are the good elements of a nation or region that draw immigrants to that location.

Pull factors are factors that encourage people to migrate to a region or country. 

A political refugee does not have to be strictly a person whose individual politics are no longer welcome in their native country. Instead, anyone who flees a negative or harmful political situation can be considered a political refugee; however, a student seeking a better education is not likely a political refugee, and is in fact likely to return to his or her native country once he or she has completed his or her education.

In 1970, there were reported to be 2.9 million refugees worldwide.  In 2000, that number was reported to have increased to 24 million.  Thus, the number of refugees increased by a multiple of about 8.

Refugees are defined as people who are being forced to leave their traditional lands due to persecution or material hardship within their society. Common causes of major refugee movements are natural disasters, warfare (particularly civil war), and political alienation or persecution. All of these countries listed are major sources of refugees because they are engaged in civil and international wars or because their governments' track records on civil rights are suspect.

A “diaspora” is the name given to a community of people who are dispersed throughout the world, but retain their cultural, religious, or ethnic differences. The term is most commonly applied to Jewish people and to African-Americans in the United States.

Populations in Stage I of demographic transition have these features. Stage II features a high birth rate, decreasing death rate, and slowly increasing population growth. Stage III features a decreasing birth rate, low death rate, and rapidly increasing population growth. Stage IV features a low birth rate, low death rate, and a stagnating population. Stage V is hypothetical and features the birth rate dropping below the death rate, causing a very slow population decline.

The demographic accounting equation is used to predict population growth and future population of a country or region. It takes into account birth rates, death rates, immigration, and emigration and so is seemingly quite thorough. The problem with the demographic accounting equation is that all of these statistics (birth rates, death rates, immigration rates, emigration rates) are subject to dramatic change over time. As a result, using contemporary statistics to project into the future becomes a dubious proposition.

The physiological population density of a country refers to the number of people in that country divided by the size of arable land in that country. It essentially refers to how much land is being used to provide sustenance for the population of a country. It is different from arithmetic population density, which simply refers to the number of people in a country divided by the size of the total land area of that country.