_The Productive Age and the Unproductive Age._--The distinction of the productive age from the unproductive age is a matter of great importance. The former extends from the age of 15 to the age of 65; the latter, the unproductive age, comprises the years before the age of 15 and those after the age of 65. Certain other classifications of the population, such as the distinction of those of an age for school-attendance from those at other ages (those of the former age comprising about one-sixth of the population), and the distinction between youthful and adult criminals, are of no interest in relation to our special inquiry.
_Classification of the Population according to Age._--In the civilised countries of modern Europe, persons at ages of 0 to 10 comprise about 24 per cent. of the population; those at ages 10 to 20 comprise about 20 per cent.; and those at ages 20 to 30 comprise about 16 per cent. of the population. Those under the age of 15 years comprise about 30 per cent. of the population, each year of life corresponding to from 2 to 3 per cent.; infants (those under 1 year) making up 3 per cent., and each year of life after that only a little more than 2 per cent. At all ages under 15 the boys are more numerous than the girls.
The age-pyramid of the population has a form which depends upon the birth-rate. When the birth-rate is higher, or the excess of births over deaths greater, the base of the pyramid is comparatively wide. Thus, in the majority of the civilised states of Europe, about 30 per cent. of the population consists of those under 15 years of age; but in France, where the birth-rate is exceptionally low, those under 15 years of age comprise a much smaller proportion of the total population.
In the country districts, the age-class of the children and the age-class of the old both contain proportionately larger numbers than the same age-classes in the towns. In the large towns and the manufacturing districts, there is an especially large proportion of persons of about 20 years of age. There are three reasons for this: first, the birth-rate is higher in the country districts; secondly, there is a drift from the country to the towns of persons of an age to earn a living; and, thirdly, a proportion of those who have grown old in the towns find their way back to the country.