The term 'population' is most commonly used to refer to the total number of inhabitants of a place, be it a town, a region, or a country. However, it is more generally used to refer to the total number of units (not necessarily people) that make up, or belong to, a group of interest. Thus, for example, it may refer to the total number of men or women in Australia, the number of children in a particular State or Territory, or even the total number of children attending a particular school. There are numerous ways in which people can be classified and counted to form population groups. They can be counted according to their country of birth, employment status, occupation, income, health status, their attitudes to issues, their experience of particular life events and so on, or indeed, on the basis of any combination of attributes that may be of interest (e.g. older women in rural areas who cannot speak English well). The choice simply depends on the issue of concern and many such choices are described in the subsequent chapters of this book.
There are, nonetheless, many social and economic issues that specifically demand regular information about the overall size, growth, structure and distribution of Australia's total population. Similar information is also needed for the population of particular administrative areas, such as the States and Territories, and the population of particular groups, most notably Aboriginal and Torres Strait Islander (Indigenous) people. In addition, information on the size, structure, and distribution of the population is needed for the practical matter of conducting social surveys both in terms of determining their sample sizes and in benchmarking their results in order to obtain aggregates that relate to actual numbers of people.
It is for these reasons that 'population' has been identified as an area of concern in its own right. The focus is on information that describes the dynamics of population change and, from the knowledge gained, providing statistics about the current and likely future size of the population. Changes in the demographic structure of the population and in its geographic distribution are also key aspects of this area of concern.
THE OFFICIAL AUSTRALIAN POPULATION
The official measure of the population of Australia is based on the concept of 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.
In terms of geography, the official population relates to the Commonwealth of Australia which includes the territories of Christmas and Cocos (Keeling) Islands but excludes external territories such as Norfolk Island and the Australian Antarctic Territory.
The size of a population, which simply refers to the number of units within the group, can be determined by taking a census. However, it is also vital to know whether the population is growing in number or not, whether the rate of change is fast or slow, and what the likely size of the population will be at various times in the future. Information about growth is greatly facilitated by having data on births, deaths and migration. Each of these components may themselves be monitored over time and analysed to help predict future events.
By tradition, statistics on population structure largely revolve around descriptions of the age and sex composition of the population. These descriptions involve the use of age-sex pyramids and summary indicators such as sex ratios and median ages. These particular dimensions are useful from a planning perspective because many human needs are associated with these characteristics. Schools and age care services are obvious examples of needs associated with age. However, both age and sex are also important structural variables used in preparing population estimates and projections. This is because the events associated with changes in population size (births, deaths and migration) are also closely associated with people's age and sex. It is by using age-sex specific rates of fertility, mortality and migration that more refined estimates of likely future trends in population growth and likely future population sizes can be provided.
There are of course many other dimensions by which the structure of a population can be defined. These include race, ethnicity, country of birth, languages spoken and religious affiliation, all of which help to describe the different cultural backgrounds of members of the population. Certainly information about the distribution of people across such groups can be provided in great detail whenever a census is conducted. However, while there are always some demands for more frequent estimates of the size of various groups than is available from censuses, such estimates are only produced where the demands for such information are high.
The distribution of the population between locations, be they cities, towns or rural areas, accessible and remote areas, or particular administrative areas, defines the spatial dimension in which human needs must be met. Population statistics are concerned with describing the size of the population of each place and the flows of people between places that influence their growth or decline. Data on the number of people for almost any area of choice (based on aggregates of census collection districts) can be obtained from each national Population Census. However, the geographic areas for which intercensal estimates and population projections are produced as a matter of course are limited for reasons related to data quality and the need to be pragmatic in terms of expected usage of the estimates.