Depending on where people live (urban or rural), how old people are (dependency ratio, younger population, graying population) and what stage of the Demographic Transition Model (DTM) a country is in, population distribution is affected in many ways.
60% of the world’s population lives in Asia. Most of those countries are predominantly rural, but many are becoming more urbanized.
Do these countries import or grow more food to feed a growing population? Is farming becoming more mechanized? As more people are moving into cities, are they improving infrastructure to handle booming cities?
If you have a younger population, are policies (education, job growth) being implemented to help in the future? If you have a graying population, like Japan, are investments being made in healthcare, retirement homes, social security? How does this put a burden on people of working age (16-64)?
The dependency ratio is the ratio of nonworking members (those under the working age and retired) to the number of working adults. The size of the dependency ratio of a country affects its economy. If a country has a high percentage of people under working age, it should invest in things like childcare, schooling, education, job growth.
If it is becoming more urbanized it should invest in jobs in services and industry. If it has a graying population, which is a large percentage of people over 64, it should invest in medical technology and personnel, healthcare, adult housing, social security.
Countries that are pro-natalist are encouraging people to have more children. Japan has invested millions of dollars into this as it is in stage 5 of the DTM. Its population is declining. In places like Eastern Europe and Singapore countries are trying to produce a population growth.
While countries in Stage 2 of the DTM (Sub-Saharan Africa) the population is rising quickly. In some of these countries the average TFR is over 5. These countries should work to improve women’s health and education, which has been able to slow natural increase rates down significantly.
Overpopulation can severely affect areas environmentally and deplete natural resources. This is the idea of carrying capacity, which is the greatest amount of people the environment of an area can support sustainably.
The more people in an area the more pollution and waste are produced. The 20 most polluted cities in the world are all in Asia.
Also, the more people there are, the more resources are being used. The Aral Sea in Central Asia, which has been used for years for irrigation, is now a fraction of the size it used to be.