The easiest way to figure this out is with vocabulary: primarily income vs. product. We know from the prefix in- that income deals with what is coming into the country. That leaves us with either Gross Domestic Product or Gross National Product. However, Gross National Product deals with the market value of the goods that have been produced by a country, not the actual amount of goods. Think of the two as quantitative vs. qualitative; GDP deals with how many goods were produced, while GNP deals with how much those same goods are worth. 

Stage 4 of demographic transition is the result of industrial and economic development and is characterized by a low and stabilized birth rate and a low and constant mortality rate. Countries that have undergone their industrial revolution and have adequate public health and education infrastructure such as Japan, the United States, and the United Kingdom are in Stage 4 of demographic transition.

Stage 2 of the demographic transition begins right before population expansion and continues until the near end of a country's industrialization process. Ghana is a country that is beginning to industrialize, and its public healthcare and education infrastructure are severely underdeveloped, which is typical of a country in Stage 2. The result is a consistently high birth rate along with an exponential decrease in the mortality rate.

This is the definition of Gross Domestic Product (GDP). Gross National Product (GNP) is GDP plus any net income from trade. The Human Development Index (HDI) measures the status of life in any given place based off of life expectancy, education levels, and income per capita. The GINI Index measures the economic inequality of a given area. Purchasing Power Parity (PPP) tries to equate relative values of difference currencies to make other measures of economic success equal to all currencies.

Of these regions Western Europe and North America score by far the highest on the Human Development Index, although it is worth noting that some countries (like Japan) in the other regions also have very high scores on the Human Development Index. Western Europe does tend to edge out North America, primarily as a result of higher life expectancy.

The Human Development Index was created by the United Nations Development Program in 2010. Its main goal is to try and de-emphasize the focus on productivity as the primary measure of development. Instead it focuses on income, education, and life expectancy. Generally speaking, the Human Development Index matches quite closely with the Gross National Product, but there are several notable exceptions such as the Middle East and Southern Europe.

Developing nations tend to have higher infant and child mortality rates. These high mortality rates are counterbalanced with higher fertility rates. Developing nations have lower literacy rates, lower incomes, and lower economic growth. Infant mortality is considered an effective baseline for measuring not only the quality of healthcare in a country, but also the overall quality of social services. Developing nations are so named in contrast with "Developed" or more wealthy nations, it does not necessarily refer to that nation experiencing economic growth.

Sub-Saharan Africa has an HDI of only 0.4, the lowest of any region in the world. All other developing regions rank at a 0.5 or higher. Russia is the highest ranking of all the regions the UN deems as "developing" with an HDI of 0.72.

Why is Sub-Saharan Africa ranked so low? The answer is that their life expectancy is the shortest of anywhere in the world.  There are many factors that cause the life-expectancy and overall health to be so low in Sub-Saharan Africa. The major cause for this is the AIDS epidemic which is a major crisis for this region of the world. Although the UN and other Government and Non-Government organizations have been helping with the AIDS crisis, it is still an incurable disease which has spread rapidly throughout Sub-Saharan Africa and continues to be the number one cause of death in this region. With many children being born with AIDS passed down from their parents, it is a challenge to get this crisis under control.

Lack of clean drinking water, lack of medical services, and minimal access to knowledge also influence the low life-expectancy and health in this region.  With many people being contaminated with various diseases and viruses from their drinking water, combined with a shortage of medicines and medical facilities to treat patients in, unfortunately many people in this region die at a young age from otherwise curable illnesses. The minimal access to knowledge and low school attendance in areas that do provide education only worsens the problem as people are not educated on how to avoid getting sick and what to do to treat an illness. Providing access to education could prevent many deaths and help begin to contain the spread of the AIDS virus.

The human development index (HDI) is calculated based off three indices: life expectancy index (LEI), education index (EI), and income index (II). The only answer choice that is not directly involved in any of the three indices is "higher cost of living." The HDI helps to classify countries into four tiers of human development.

According to the Demographic Transition Model, Stage 1 is defined by very high birth rates and death rates. As countries transition to Stage 2, the death rate begins to fall, while the birth rate lags and continues to remain high. In Stage 3, the death rate falls more slowly while the birth rate falls steadily. Moving into Stage 4, the birth rate falls more slowly and the death rate is low and stable. In Stage 5, the final stage, death rates remain low and birth rates may drop further, leading to a slow decrease in population.