The median age in the United Kingdom is about 40 years.
Median Age is closely related to fertility rate.
Maps from Wikipedia: Median Age , Fertility Rate
Learn the basics of measuring population.
If a country has a high fertility rate or birth rate, the median age will be low. At a fertility rate of around 2 per female, the population will be steady and have roughly the same number of people in all age brackets (except those that die.) However, at much higher fertility rates, the population multiplies in each generation.
The average Nigerian woman has 5 children, and this is why the population doubles every generation. In Niger, which has the highest fertility rate in the world at almost 8 children per woman, the population about triples every generation.
While some populations are ageing (see Canada, Japan, and most of Europe on the maps), some countries are getting younger (particularly in Africa).
With a VOTING AGE of 18 in Nigeria, half of the population is (by law) too young to vote. By comparison, only 20% of the UK population is too-young-to-vote.
I think the voting age in countries (like Nigeria) that have young populations should be lowered so that majority of citizens can vote.
