The population pyramid or demographic pyramid as it is also known, is the graphic representation of the distribution by age and sex of the population. Graphically it consists of a double frequency histogram, arranged horizontally, indicating the points of the male population (on the left) and the female population (on the right).
The characteristics of the population structure will depend on the factors of demographic dynamics: mortality, fertility and migration. The combination of these three factors, as well as the size of the population, are determining factors in the description of the population.
There are three types of population pyramids:
Progressive population pyramid, presents a wide base, compared to superior groups that are decreasing, as a result of a high birth rate and progressive mortality according to age; indicating an extremely young population structure with growth expectations. This kind of pyramid is associated with underdeveloped countries, due to their high mortality and high birth rates.
Stationary population pyramid, a harmony between all age groups is appreciated, as a consequence of a birth rate and mortality, without significant variations over a long period of time. This pyramid is related to developing countries.
Regressive population pyramid, it is wider in the upper groups than in the base, this is due to the decrease in the birth rate and the continuous aging of its population, so its hope for the future is decreasing. This pyramid corresponds to the developed countries.
There are other forms of pyramids such as those that show mortality or low birth rates, as well as those that show the high population of women than men.
Population pyramids are of great importance as they provide the updated demographic history of a specific country in their form.
To develop a population pyramid, it is necessary to have all the information regarding the population of a certain territory, classifying them by age and sex, these data can be obtained through population censuses.
This graph is designed based on a vertical and a horizontal axis. The ages are placed on the vertical axis of the pyramid. Generally, when a population pyramid is made, groups are set with spaces of 0 to 4 years, 5 to 9 years, 10 to 14 years, etc. Always placing the younger ages on the base of the graph and the older ones at the top.
On the horizontal axis, the number of population is placed depending on sex: on the left side of the axis are the data for males and on the right side the data for females.
On this structure and taking the data of the population of a specific region and of a determined space of time, we proceed to construct the horizontal bars, placed one above the other for each age group and sex.
Regarding the interpretation of the pyramid, the first thing is to recognize the type of pyramid, that is, if it is progressive, stable or regressive. This makes it possible to identify the behavior of birth and mortality, as well as the rate of growth and decline of the population; this is done by comparing the width of the base and the top of the pyramid
