Age Structure (age pyramid), breakdown of the population by age groups, one of the chief characteristics of a population. It is derived from the number of births ( Birth Rate), the number of deaths and ages at death (mortality) and international in-migration and out-migration ( Migration). It serves as a basis for determining the proportion of individuals of retirement age, children of school age and kindergarten age, women of childbearing age, and the manpower potential. Currently (1996) 17.4% of the Austrian population is in the age group of 0 to 15 years, 62.9% is between 15 and 60, and 19.7% older than 60 years. The share of persons 60 and over is expected to rise rapidly in the next few years, while the share of persons aged 0-15 years will decline.