Answer:
Population Shrinkage (or Population Decline)
Explanation:
It can be used to refer to long-term demographic trends, such as urban decay or rural exodus, but is also commonly used to describe large population reductions due to violence, disease or other disasters. A good example is Japan, where the young population is small in contrast to a huge elderly population. In this case, the Population Shrinkage is caused by the less of birth, and the populational control executed by the Japanese government.
