Key issue # 3: Why is population increasing at different rates in different countries?

Answer:
A country moves from high birth rates and death rates, with little population growth, to low birth rates and death rates, with low population growth. During this process, the total population increases dramatically because the death rates decline before the birth rate does. The MDC's have slower growth rates while the LDC's have a period of rapid population growth.

Summary:
All countries have experienced some changes in NI, fertility, and mortality rates, but at different times and at different rates. A similar process of change in a society's population is occurring known as the Demographic Transition.

Demographic Transition:
This process has several stages, and every country falls into one of them.
-Stage 1: Low Growth: There are very high birth rates and death rates. The burst of population in 8,000 b.c was caused by the agricultural revolution, which was the time when humans first domesticated plants and animals and no longer relied entirely on hunting and gathering.
-Stage 2: High Growth: There are rapidly declining death rates combined with very high birth rates. This produces a very high NI. Countries entered stage 2 after 1750 due to the Industrial Revolution, which led to a series of improvements in industrial technology that transformed the process of manufacturing goods. Also, the Medical Revolution in the 20th century pushed many countries into stage 2. Medical technology spread to the poorer countries and helped eliminate the traditional causes of death.
-Stage 3: Moderate Growth: Birth rates rapidly decline, death rates continue to decline, and NIR begins to slow.
-Stage 4: Low Growth: There are very low birth/death rates, no longterm NI, and possibly a decrease. In this stage the CBR= CDR, and the NIR reaches zero. This condition is known as zero population growth.

Population Pyramids:
Population in a country is influenced by the Demographic transition in two ways- the percent age of the population in each age group and the distribution of males and females. This info can be displayed on a bar graph called a population pyramid. The shape is mainly determined by the CBR. The most important factor of age distribution is the dependency ratio, which is the number of people who are too young to work compared to the number of people in their productive years. The number of males to females in the population is the sex ratio. In general, slightly more males are born than females.

Countries in the Different stages of the Demographic Transition:
Countries display different population characteristics depending on their stage in the demographic transition. There are no countries today that remain in stage 1.

Demographic Transition and the World Population Growth:
There are many countries in stage 2 or stage 3 of the demographic transition. These countries have a rapid population growth and only a few of them are likely to reach stage 4 in the near future.

Article:
http://en.wikipedia.org/wiki/World_population

In this article, it explains that MDC's have better technology and health standards, therefore they are able to control their population. But in may LDC's in Africa, they are unaware of the consequences and they do not have the same beliefs. For example, in the MDC's there are medicines and vaccines to treat illnesses and viruses. However, in LDC, they do not yet have the technology to produce these preventatives. These are a couple of the reasons explained in the article that affect population rates.