A population pyramid is a powerful tool for visualizing and comparing a population’s age and sex composition. It is a bar chart, arranged vertically, that shows the distribution of a population by age and sex. It gives a good graphical illustration when the population is growing of a region, country or of the world. The diagram used in a population pyramid is constructed from numbers from the national census returns. Males are on the left of the pyramid and females are on the right. The younger ages are shown at the bottom. As older populations are thinned out by death, it is represented by a progressive narrowing toward the apex of the pyramid (Getis 120). Migration affects the shape of the pyramid, because most migrants are shown in the working ages. Usually, more males migrate across national borders than females (Human Population). Birth and death rates determine the basic pyramid shape.
The purpose of a population pyramid is to show the population breakdown by age and gender in a graph. A country’s present and past mortality and fertility trends are reflected by age structures. Insights into a country’s national political and economic challenges can be provided by age structures, now and in the future (Leahy).
Some of the things that a population pyramids show are birth, death, fertility, migration, and growth rates. It also shows the net migration rate and the number of migrants. They also foretell problems resulting from present population policies or practices (Getis 122). Population pyramids are the most effective way to portray age and sex distribution of a population, in a graph. They are often used because they give you a clear visual image.
In figure 1, is a capture of the population pyramid for Nigeria, 2012. This population pyramid shows the age and sex structure of Nigeria. It provides insights about economic development and social and political stability. Looking at the graph, males are shown on the left and females on the right. The horizontal bars represent five year age groups of the breakdown of the population. The youngest age groups are at the bottom and the oldest at the top. Nigeria’s population maintains the classic pyramid shape of a very youthful population. The shape of the pyramid gradually evolves over time based on fertility, mortality, and international migration trends (Leahy).
Figure 1. Population pyramid of Nigeria, 2012 that shows the age and sex structure. Source: “World Population.” U.S. Census Bureau. U.S. Department of Commerce.
Nigeria is in the early stages of the demographic transition, because it is well within the category of a very young age structure. Three-quarters of its population is under the age of 30. The death rate is declining, while they continue to have a high birth rate. This causes the population to expand, creating population growth. Nigeria’s population has grown more unbalanced in recent decades. The population of young people increased, while the older adults slightly decreased between 1975 and 2005. This reversed Nigeria’s course along the path of the demographic transition. This irregularity is the process of most countries’ development (Leahy).
This regression, along the demographic transition of Nigeria, can only be explained by its declining birth rate and stagnant death rate. There has barely been any change in mortality rates since 1975. It changed from 20 to 19 annual deaths per 1,000 people. Total life expectancy is 44.3 years for women and 44.1 years for men. That’s a decline from previous decades. Between 1975 and 2005, the total fertility rate dropped from 6.9 to 5.9 children per woman. As fertility and mortality rates have remained high, the momentum of population growth has led the share of children and adolescents within the population to increase. This made Nigeria’s age structure even more unbalanced than it was (Leahy).
I chose New Zealand to compare to Nigeria’s population pyramid because they are so different. In the population pyramid below, New Zealand exemplifies a stable population structure (Getis, 121). New Zealand is a wealthy country with a very slow growth rate. The population is nearly equally divided among the age groups, giving the pyramid almost vertical sides (Getis, 120).