what is age composition? how does it affect the population's economic and social structure?

Age composition is the composition of different age groups of the population in certain groups.For example, there are three age groups they are :-

1.Children(0-14 yrs)

2.Working population (15-59)

3.Aged (60 and above)

Age composition determines the working capacity of the population, the liability it possesses,etc.

Looking at the age structure you can quickly tell whether the population is increasing.
A population that is holding steady will have equal numbers for all ages.
A population that is increasing will have more children.
A population that is declining will have fewer children.