Population is defined as all nationals present in, or temporarily absent from a country, and aliens permanently settled in a country. This indicator shows the number of people that usually live in an area. Growth rates are the annual changes in population resulting from births, deaths and net migration during the year. Total population includes the following: national armed forces stationed abroad; merchant seamen at sea; diplomatic personnel located abroad; civilian aliens resident in the country; displaced persons resident in the country. However, it excludes the following: foreign armed forces stationed in the country; foreign diplomatic personnel located in the country; civilian aliens temporarily in the country. Population projections are a common demographic tool. They provide a basis for other statistical projections, helping governments in their decision making. This indicator is measured in terms of annual growth rate and in thousands of people.

The youth population is defined as those people aged less than15. The share of the dependent population is calculated as total elderly and youth population expressed as a ratio of the total population. The youth-dependency ratio relates the number of young persons that are likely to be dependent on the support of others for their daily needs to the number of those who are capable of providing such support. Demographic trends have a number of implications for government and private spending on pensions, health care, and education, and, more generally, for economic growth and welfare. This indicator is measured as a percentage of population.

The elderly population is defined as people aged 65 and over. The share of the dependent population is calculated as total elderly and youth population expressed as a ratio of the total population. The elderly dependency rate is defined as the ratio between the elderly population and the working age (15-64 years) population. The comparability of elderly population data is affected by differences, both within and across countries, in how regions and the geography of rural and urban communities, are defined. Elderly people tend to be concentrated in few areas within each country, which means that a small number of regions will have to face a number of specific social and economic challenges due to population ageing. These demographic trends have a number of implications for government and private spending on pensions, health care, and education and, more generally, for economic growth and welfare. This indicator is measured as a percentage of population.

The total fertility rate in a specific year is defined as the total number of children that would be born to each woman if she were to live to the end of her child-bearing years and give birth to children in alignment with the prevailing age-specific fertility rates. It is calculated by totalling the age-specific fertility rates as defined over five-year intervals. Assuming no net migration and unchanged mortality, a total fertility rate of 2.1 children per woman ensures a broadly stable population. Together with mortality and migration, fertility is an element of population growth, reflecting both the causes and effects of economic and social developments. The reasons for the dramatic decline in birth rates during the past few decades include postponed family formation and child-bearing and a decrease in desired family sizes. This indicator is measured in children per woman.

The working age population is defined as those aged 15 to 64. This indicator measures the share of the working age population in total population.

The old-age to working-age demographic ratio is defined as the number of individuals aged 65 and over per 100 people of working age defined as those at ages 20 to 64. The evolution of old-age to working-age ratios depends on mortality rates, fertility rates and migration. OECD countries have seen prolonged increases in life expectancy that most analysts project to continue, implying an increasing number of older people and most likely of pensioners too. This indicator is meausured as a percentage.