Zero Population Growth

The state whereby the number of individuals in any given group remains constant with time. This happens when the birth rate plus immigration equals the death rate plus emigration. The rate at which people must reproduce in order to ensure a natural (as opposed to overall) ZeroPopulationGrowth is called the generation replacement level and is estimated at around 2.1 children per woman. Many developed nations have significant negative population growth.

In the cases of Germany, Italy and Sweden, this is due to low fertility rates (1.37 children per woman for Germany, and 1.21 for Italy) and immigration is used to maintain pseudo-stable population levels. Note that all member states of the council of Europe have a fertility rate below the generation replacement rate. So if they did not have net immigration, then their populations would fall.

In the cases of Russia, the Ukraine, Bulgaria, Hungary, Estonia and Latvia, this is due to their collapsed economies which have raised the mortality rate and lowered life expectancy. (http://www.mic.org.mt/PR%27s/eurostat/No.96.htm)

Outside of Europe, Japan has a population growth of 0.17% and falling (most Western countries have a rate around 1%) and its population should peak in 2010, after which it will decline.

Although perhaps not actively thought of as such, ZPG is also crucial for computation with finite resources. A program running in limited memory space must ultimately attain ZPG with respect to memory utilization. By analogy, GarbageCollection is effectively what determines the death rate of formerly utilized memory.

Question for the original author: Do any of these studies you mention examine what the population decline is due to? Last I'd heard, one was not only expected but encouraged, due to the unnatural spike in population during the post WorldWar2 baby boom. The decline is due to boomers and children of boomers choosing not to have children of their own, for whatever reason. Usually because they have high enough expenses and little enough space as-is. Overall, a world reduction in population to a stable point (presumably, the point at which expenses and space make couples feel like having exactly two children) sounds like a good thing.

AnswerMe

Not an answer, but a correction: I believe that the "Baby Boom" is largely an American-only phenomenon. Americans could come back home and reproduce; Europe had countries to rebuild..."

Yes, but I think there was still a population spike in Europe and Japan, wasn't there? Different causes, but the same effect at about the same time.

Europe definitely had a population spike after the war. Combined with the current reduction of the active population (less births), this is putting huge stress on the pension systems of many European countries. Governments are starting to take measures, but they're usually not very well accepted by the public (France is going through a series of strikes currently because the government is proposing to increase the pension age.

At least in Sweden, the actual term "Baby Boom" is used for this post-war nativity bump.

We use the same term in NewZealand and Australia. Like the US and Canada, NZ and Oz had little or no fighting on their own soil, and sent warriors to Europe, Asia, and Africa. The page <http://www.abs.gov.au/Ausstats/abs%40.nsf/94713ad445ff1425ca25682000192af2/bdda207cf3d7349aca256cae00053fa9!openDocument> includes a graph of the Australian birth rate in which the bump is quite visible.

A further correction: The BabyBoom? in the UnitedStates was actually a temporary return to the UnitedStates' historical population growth rate. From its colonization until WorldWarOne?, the UnitedStates' natural population growth rate was about 2.5 % per year, and its immigration rate was about 0.8 % per year. Immigration dropped off dramatically at the beginning of WorldWarOne?. The GreatDepression and WorldWarTwo? caused young people to postpone marriage; the birthrate dropped. After WorldWarTwo?, peace and prosperity allowed Americans to form families at historical rates. In the UnitedStates, the so-called "Baby Boom" ended with The Pill, the Sexual Revolution, and the legalization of abortion.

CategorySociety