The regressive population pyramid is a type of population or demographic pyramid that is observed mostly in developed countries and in those where the largest population is older-adults (aged countries), for different reasons, such as the massive exodus of young people., high mortality in young people, among others.
Among its main characteristics are: that it is wider in the groups that start in the center and end at the top, that is, the oldest. Its base (the place where younger people are located) is narrower, thanks to the decrease in the birth rate and the constant aging of its population. For this reason, the outlook for its future is in decline, with zero or negative growth.
A population or demographic pyramid is a graph formed by bars that increase and decrease horizontally and is made to show the number of citizens that exist in a population at a given time, which are divided by age range and sex, starting with newborns and babies at the bottom and the elderly (elderly) at the top.
The existing male population is located on the left side of the pyramid, while women are located on the right side of the pyramid. The age division is carried out in what is known as quinquennial, that is, the ranges go from five to five years. It starts at zero to four years of age, then five to nine, and so on.
In that sense, there are three types of pyramids: progressive, stable and regressive.
Population pyramids make it possible to make annual comparisons of the behavior of a country's population and analyze its evolution over time. These allow even creating tables of percentages of population groups, to make a statistical division, where by finding the number of citizens in a range that includes two or three bars of the pyramid, a percentage can be returned. For example, from 0 to 14 years of age, the population comprises 23% of the total.
The number of people in the age ranges respond to demographic dynamics, where they vary according to the rates of birth, mortality, emigration and immigration that the country handles.
