# Growth and Decay, Population Change

Growth and decay refer to the direction in which a quantity is changing. If something is growing, it means that a value is increasing (example–world population growth over time). If something is decaying, it means that a value is decreasing (example–population of Japan is decaying over time). A growth or decay factor describes the rate at which a quantity is changing over a certain period of time via a multiplication sequence (factor implies multiplication). For example, to describe a population increase by 10%, multiply by the growth factor 1.10. To describe a population decrease by 10%, multiply by 0.90 (shows a 10% decrease because only 90% of the theoretical population is remaining. A total change is the amount by which a quantity increases or decreases–for example, the total population change for Japan from 2010 to 2016 was a population decrease by 1.13 million (128.06 million in 2010 –> 126.93 million in 2016). The percent change for this population from 2010-2016 would be a 0.88% decrease in population. The average rate of change would be decreasing by .18 million people per year (this means the population is decreasing by less than a quarter of a million people per year). The terms linear growth would refer to a steady decrease per year, resulting in a linear graph while exponential growth or decay means that a quantity is increasing more and more rapidly or decreasing more and more rapidly over time.

See the data for Japan population decay here.

## 4 thoughts on “Growth and Decay, Population Change”

1. Interesting subject and good explanation of growth and decay. Sophomore year I wrote a paper on aging and population decline in Japan so I’m somewhat familiar with the topic. From my understanding, one of the largest factors contributing to the issue is the harsh nature of working in Japanese society. Hours are often cutthroat and competitive, and times spent outside of work are often just to relax, leaving little time for family, or finding a spouse. Hopefully Japan finds some sort of way to remedy the problem, as it could have drastic consequences for their standing in the world if their population keeps decreasing.

2. I think you did a good and clear job explaining decay and growth rates and how to find them! It’s interesting to see the growth and decay of population for countries all over the world.

3. This is very interesting. I think that japan is heading in the right direction. The world is heading to a unprecedented amount of people that is not sustainable.If Japan can show linear decay in population maybe that gives hope for the mega countries trying to limit population like china. I wonder what the correlation is between the decay of population in japan and the amount of pollution the country regularly emits. I hope that the pollution is decreasing as well.

4. I agree with everyone else. I think that you did a really good job explaining growth and decay in terms of Japan’s situation. It’s interesting to see how different countries have different population patterns.