**GLOSSARY**

**Ageing of the population**

Ageing of the population is the consideration of the proportion of the population aged 65 years and over, and the way this proportion is continuing to increase, mostly due to persistent low fertility rates and declining mortality rates.

**Average annual rate of growth**

The average annual growth rate, r, is calculated as a percentage using the formula:

where P_{0} is the population at the start of the period, P_{n} is the population at the end of the period and n is the length of the period between P_{n} and P_{0} in years.

**Census count**

The Census of Population and Housing enumerates persons on the basis of where they were located on census night. Characteristics of households are only available according to place of enumeration. The census also compiles information on people according to their place of usual residence. This information is coded to Statistical Local Area. This means that census counts of people can be produced according to their location on census night as well as their place of usual residence.

**Estimated resident population (ERP)**

The official measure of the population of Australia is based on the concept of usual residence. It refers to all people, regardless of nationality or citizenship, who usually live in Australia, with the exception of foreign diplomatic personnel and their families. It includes usual residents who are overseas for less than 12 months. It excludes overseas visitors who are in Australia for less than 12 months.

**Intercensal discrepancy**

Intercensal discrepancy is the difference between two estimates at 30 June of a census year population, the first based on the latest census and the second arrived at by updating the 30 June estimate of the previous census date estimate with intercensal components of population change which take account of information available from the latest census. It is caused by errors in the start and/or finish population estimates and/or in estimates of births, deaths or migration in the intervening period which cannot be attributed to a particular source. For further information see __Population Estimates: Concepts, Sources and methods, 2009 (cat. no. 3228.0.55.001)__.

**Life expectancy**

Life expectancy refers to the average number of additional years a person of a given age and sex might expect to live if the age-specific death rates of the given period continued throughout his/her lifetime.

**Mean age**

The average age of the population.

**Median age**

For any distribution the median value is that which divides the relevant population into two equal parts, half falling below the value, and half exceeding it. Thus, the median age is the age at which half the population is older and half is younger.

**Population growth**

For Australia, population growth is the sum of natural increase and net overseas migration. For states and territories, population growth also includes net interstate migration. After the census, intercensal population growth also includes an allowance for intercensal discrepancy.

**Population projections**

Population projections are not predictions or forecasts. They are an assessment of what would happen, in future years, to Australia's population given a set of assumptions about future trends in fertility, mortality and migration.

**Sex ratio**

The sex ratio relates to the number of males per 100 females. The sex ratio is defined for the total population, at birth, at death and among age groups by appropriately selecting the numerator and denominator of the ratio.

**Usual residence**

Usual residence within Australia refers to that address at which the person has lived or intends to live for a total of six months or more in a given reference year.

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