In my Population Statistics class we learned that Japan, Italy, and Germany have the three oldest populations (A lot of old people, not as many young people, and declining populations). Does this have anything to do with either World War Two or its aftermath, or is this just a coincidence?
Coincidence, at least nowadays.
People fighting in WW2 were born roughly 1900-1930, they would be at least 84 years old now.
There are multiple factors for this, including the great healthcare those countries provide. It's better to be 80 years old in Germany or Japan than in Ukraine or Zimbabwe, thus a lot of older people live longer and healthier.
Economists often attribute the opportunity costs of having children to this phenomenon. 100 years ago children were the social insurance/pension fund of families. They took care of the parents once the became old and were necessary to survive. Nowadays one does not need a child, because social security is provided by health insurance/pensions funds etc.
So many couples decide to only have 1-2 children, because they are expensive.
Another huge factor is the availability of birth control and the social acceptance of having sex for pleasure only and the acceptance of being a family without having children.
The statistic for Germany shows the decline of the birth rate beginning in the 1960s: http://upload.wikimedia.org/wikipedia/commons/0/0e/Bevoelkerungsentwicklung_deutschland.png (blue line: birth rate, green line: death rate)
Correlating with this phenomenon (there might also be causation) is the decline of religion in Germany. Religious Christian families tend to have more children then atheists or not obeying Christians.
Less than 2% of families with children in Germany have more than at least 4 children nowadays. http://www.bpb.de/nachschlagen/zahlen-und-fakten/soziale-situation-in-deutschland/61597/haushalte-nach-zahl-der-kinder
Well I don't know the reasons behind Italy and Germany's declining population, but I do know that Japan's population crisis is more a result of social structures revolving around work and family obligations.
What's happening right now is that young people in Japan are just not getting married and having kids. For women, getting married and having kids is usually accompanied by social pressures to give up the jobs and careers (partly because the amount of time/dedication that most people put into their jobs is super demanding, and partly because of the traditional roles of family). Many women are opting out entirely, not wanting to give up their careers. In the same way, many men are opted out because the added stresses of family seems to outweigh the benefits. That coupled with the population's overall longevity is creating the older population and population crisis. Additionally, Japan's tight policies on immigration don't allow population growth through their immigrants.
So I don't believe it's related to WWII in Japan's case, but I don't know enough about Germany and Italy to speak on their populations.
Well, I guess it's more accurate to say that WWII plays a slight role. For example, it's thought that the dietary privations faced by Okinawans during WWII play a role in the longer life expectancy there. Technically, Okinawa wasn't part of Japan between 1945-1972, though. Slightly lower than normal calorie consumption has been shown in some studies to extend life.
Interestingly, all 3 countries were extremely pro-natalist during the war, and then swung the other way towards fewer children as the years have gone by.
I think ultimately it's a coincidence. The conditions in the 3 nations have been too radically different, including Germany having been 2 countries for most of the time.
