The following are definitions of some basic terms used frequently within population geography.

Natural Increase - The rate, at which a population increases, basically birth rate minus the death rate, and excluding immigration. This number is usually expressed per 1000 of the population, and may be expressed as a percentage.

Birth Rate- The number of births annually within a country or realm. Usually expressed by numbers of births per one thousand of the population, and may be expressed as a percentage.

Death Rates - The number of deaths annually within a country or region. Usually expressed by numbers of death per one thousand of the population, and may be expressed as a percentage.

Infant Mortality Rates - The number of deaths within a country or region, age 1 or below. Usually expressed by numbers of deaths per one thousand of the population, and may be expressed as a percentage. If infant mortality rates are considered in life expectancy rates and are high, it may impact the numbers significantly.

Life Expectancy Rates - The number of years a newborn can expect to live, calculated annually. Usually expressed as a percentage.

Population Density - The number of people per square mile or kilometer, usually takes total population of a country or region and total area. Can vary dramatically within a state, an example is density figures for Tokyo and all of Japan.

Double Time - The number of years it would take for a population to double in size if it continues to grow at the current rate.

Migration - permanent movement of the population. May be voluntary or forced.

Immigration- migration of the population from one sovereign state to another.

Out- Migration - movement of a population out of a sovereign state, usually a result of a lagging economy or civil strife.

Median Age - the middle or fiftieth percentile in regards to age within a population.

Average Age - the sum of all ages divided by the total number of the population.
 
 

Demographic transition models are models that attempt to link economic development to changes in birth and death rates within a region or country. These models presented below should reveal a state’s ability to meet the needs of their home population, and where priorities lie in relation to governmental and economic policies. The last section presents factors that can disrupt or interrupt the application of the following stages.
 
 

Stage 1 - High Birth Rates - High Death Rates

Often found in underdeveloped realms. Factors/Conditions found in these areas are as follows: high disease rates, high infant mortality rates, low life expectancies, undeveloped medical technology or little access to medical facilities, malnutrition, and endemic diseases. Population growth overall stays static due to high death rates, and the population’s age is usually quite young, maybe as much as 60% of the population may be under 16 years of age.
 

Figure 1

Challenges for stage one category: feeding the general population, providing basic medical care, and educating a young population. Recently controlling H.I.V infection rates as proved to be a sometimes-overwhelming task within these realms.
 
 

Stage Two - High Birth Rates - Low Death Rates

Found in undeveloped realms and newly industrialized countries. Underdeveloped regions usually have via governmental policy improved medical technology to provide basic health care to the general population. Stage two regions have improved basic health care to the point of combating most endemic diseases and other disease that is commonly classified as having a cure, treatment, or immunization. Medical technology here usually does not extend to birth control, treatment of many cancers, and treatment that requires very high levels of technology or capital, such as heart disease and H.I.V. Infant mortality rates can vary dramatically in this category. Some discussion should focus on countries or realms that remain in this category not due to lack of medical technology or economic development, but rather due to religious beliefs. Often the acceptance of a religious doctrine that discourages the use of birth control will, if accepted by the majority, result in the region consistently remaining within category 2 despite levels of economic development. Good examples of this are the influence of Catholicism in Latin America, and Islam within Middle Eastern countries that have developed rapidly due to oil resources. This category is worldwide the greatest area of growth, generally this stage has a relatively young population, overall age is usually determined by the number of years it has been since transition from stage 1 to stage 2.
 

Figure 2

Challenges for stage 2 category: feeding a rapidly growing population, depending on the area of land available, there may be competition for land devoted to human occupancy and land devoted to agricultural production, meeting the educational needs of a growing population, basic medical needs for larger numbers, providing jobs for large numbers entering the workforce and often providing infrastructure in cities for a rapidly urbanizing population. In recent years combating A.I.D.s and H.I.V. has been a difficulty within these regions. An area that is barely meeting the medical and educational needs of their population is forced to divert capital towards A.I.D.s education, prevention, and treatment.
 
 

Stage Three- Low Birth Rates - Low Death Rates

Found in some areas that are newly industrialized, more often found in the post-industrialized world. Medical technology and economic development is such that life expectancies are quite high. Countries or regions that fall within this category usually have widespread use of some form of birth control. Often immigration is the primary factor behind overall population growth. Some countries have static or negative natural growth rates. Generally within this category you see the median age in the late thirties or early forties and growing older.
 

Figure 3

Challenges for category 3: providing medical care for an aging population, meeting taxation and labor needs with a shrinking base, treatment and care of a growing elderly population, immigration policies and/or legislation aimed at increasing the natural increase.
 
 

Exceptions/Interruptions

The following are factors that can interrupt or negate transition; war, fatal diseases without a known cure, religious doctrine, and famine. You may have this under the well-known heading of the "four horsemen". All of the following are capable of rendering all categories to High Birth - High Death, or Low Birth - High Death.
 
 

Exercise 1

The CIA Factbook gives a country profile on every state in the world. The following exercise demonstrates differences between a state in category 1 of the demographic transition model and a state in category 3.

Go to CIA Factbook - Country Profiles.

This takes to the country profile section of the CIA Factbook. When you enter this section click on the countries of The Democratic Republic of Congo and Japan. Compare the age structure, birth and death rates, infant mortality rates, and life expectancies and document the differences.
 
 

Exercise 2

Go to United Nations Population Information Network.

This takes you into the United Nations page on world population. When this site is contacted, click on Brief Packet World Population Estimates for 1998. Next, click on Aging, (at the bottom of the page). What region has the oldest population? Then go back to World Population Estimates and click on Demographic Impact of HIV/AIDS. What country is hardest hit by AIDS? How dramatic is the impact?
 
 

Exercise 3

Go to National Geographic.

This link will allow you to glimpse what life is like in Tanzanian Refugee Camp. After you reach link, click on "refugees".