Language & WorldFact
In some countries half the population is under 16.
Median age splits a population into two equal halves. In Niger it is around 15 years; in Japan, Italy and Germany it is roughly 45 to 49. Worldwide it is about 30. A young country mainly needs schools and jobs, an old one needs care and pension funding; the same policy won't fit both.
Useful: Before comparing two countries, check their median age; it explains a lot.
Source: en.wikipedia.org