Doubling Time
New Zealand grew at a decadal average growth rate of 1% from 1,908,310 people in 1950. According to the graph, the population reached 3,819,762 in the year 2000. Therefore, it could have doubled in the previous year 1999 to 3,816,620. Considering the formula of doubling time:
- 75/growthrate=doublingtime
- 75/1=75 years, which is around 2025
Costa Rica’s population grew at the decadal rate of 1.99% from 866,982 people in 1950. The population reaches 1,735,523 people in 1970, showing that the population might have doubled in 1969. Using the doubling time equation:
- 75/1.99*38 years, making the doubling year 1988
Mozambique’s decadal average growth rate is 3.04% and grew from 6,250,443 in 1950 to 12,666,573 in 1990, making the doubling year close to 1985. The doubling time equation gives:
- 75/3.04*25 years, with the doubling year as 1975
Qatar grew from 25,101 in 1950 to 45,183 in 1960 at the decadal rate of 15.43%. Therefore, the doubling year could have been around 1962, according to the graph. However, according to the doubling time equation:
- 75/15.43*5 years doubling time, making 1955 the doubling year
Population Graphs
The graph of high-growth-rate countries depicts a steady population increase, showing progressively growing population. The graph curves upwards to look like an exponential curve or a quarter pipe. On the other hand, most low-growth-rate countries have downward facing curves, flat ones, or straight upward then flat curves. Most of the graphs show an upward trend, then flatten or go on a downward one. Nigeria’s growth rate is 4.1%, making its doubling time equal to 75/4.1*18 years.
However, hovering over the graph shows that the doubling time is about 30 years.
Causes of Rapid Growth
The rapid growth seen in dark blue countries results from a combination of a variety of reasons. Some of them include a sudden increase in life expectancy levels, a decline in mortality rates, improved living standards, and a young reproductive population (Ritchie & Roser, 2019). Attitudes, cultural beliefs, and practices that support high fertility rates also play an essential role in rapid growth (Ritchie & Roser, 2019). For example, most African cultures link large families to economic wellbeing, perceiving children as financial assets and old age security. The pyramid shape of rapid growth countries indicates a high population of reproductive members, around half of the country.
Shrinking Populations
Shrinking populations have a lower number of reproductive members and a higher number of older generations. They also have a lower number of pre-reproductive members, indicating lower fertility rates among the reproductive group (Ritchie & Roser, 2019). The graphs have a downward trend while the pyramids are heavier at the top than at the bottom, suggesting greater numbers of older non-reproductive members and a declining young reproductive population.
Population Pyramid Shapes
The population pyramid is a good indicator of population growth and decline. It shows the percentage of each age group in the country: higher numbers of the young population indicate rapid growth and vice versa (Ritchie & Roser, 2019). Diminishing growth countries’ pyramids are heavier at the top, creating a V shape. Slow but steady growth countries have pyramids that look like straight towers, showing an almost equal number of each age group. Fast growth countries’ pyramids have broad bases and narrow down with height, indicating a larger young population.
Reference
Ritchie, H., & Roser, M. (2019). Age structure. Our World in Data.