The population forecast is based on net migration, fertility and mortality since 1985. It uses a probabilistic methodology by making 10,000 forecasts based on net migration, fertility and mortality rates since 1985.

The median figure from these forecasts makes up the forecasted population figure.

Glossary:

• Net migration is the difference of immigrants over emigrants.
• Fertility rate is the number of live births per 1,000 women.  
• Mortality rate is the number of deaths per 1,000 people.
• The ‘per 1,000 unit’ is used to account for differences in population, sex distribution, etc. This makes it possible to compare periods with e.g. different populations.
• Sex distribution is the percentage distribution between males and females.
• Index shows the year-to-year percentage change, with a base year set at 100. The difference between two years is measured in percentage points.
• Dependency ratio is the ratio of dependent young and old to the population generally considered to be of working age, those aged 16-66. When the dependency burden is 1, the number of people in the 16-66 age bracket is equal to that of the rest of the population.

See also Population, Net migration, Births and Deaths.

Methods:

From the forecasts these probability levels are extracted:

 There is a probability of 95% for the forecast population to be between lower95 and upper95

 There is a probability of 90% for the forecast population to be between lower90 and upper90

 There is a probability of 80% for the forecast population to be between lower80 and upper80

 median: The middle value