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FERTILITY AND ITS EFFECT ON AUSTRALIA'S FUTURE POPULATION AGESPECIFIC FERTILITY Over the last 20 years (19842004) the fertility of younger women declined while the fertility of older women increased, reflecting the continuing trend towards older motherhood (graph 5.26). Women aged 2024 years experienced the greatest decrease, with fertility nearly halving (down by 43%) over the period (from 94.3 children per 1,000 women in 1984 to 53.4 children per 1,000 women in 2004). Teenage fertility (women aged 1519 years) decreased by 30% (from 23.2 to 16.3), and fertility of women aged 2529 years decreased by 27% (from 140.4 to 102.5). In contrast, the fertility rate for women aged 3034 years increased by 41% (from 81.2 children per 1,000 women in 1984 to 114.4 children per 1,000 women in 2004), and the rates for women aged 3539 years and 4044 years more than doubled (from 25.0 to 57.4 and 4.3 to 10.6, respectively). However, the fertility of women aged 35 years and over has not yet attained the level observed during the baby boom nor the higher rates observed at the height of the 1920s. FUTURE FERTILITY PROSPECTS The latest Australian Bureau of Statistics (ABS) population projections (20042101) assume three future scenarios for fertility in Australia: high fertility (TFR of 1.9 babies per woman by 2018 and remaining constant thereafter), medium fertility (TFR of 1.7) and low fertility (TFR of 1.5) (see Population projections). Additional scenarios considered in this article range from a TFR of 1.0 to the replacement level TFR of 2.1. EFFECT OF VARYING FERTILITY ON FUTURE POPULATION Fertility has a steady and pronounced impact on population growth. Holding mortality and net overseas migration (NOM) constant at the medium levels specified in the most recent ABS population projections, a change of 0.1 births per woman in the medium TFR (1.7 births per woman) would result in population change of almost one mill. people (larger or smaller) by 2051 and more than two mill. by 2101. The medium projection series assumes the TFR will decrease to 1.7 babies per woman by 2018 and then remain constant, life expectancy at birth will continue to increase each year until 205051 at a declining rate reaching 84.9 years for males and 88.0 years for females, and NOM will be held constant at 110,000 per year throughout the projection period. If fertility were to remain constant at its 2004 level of 1.8 children per woman, Australia's population would reach 28.9 mill. by 2051, and 33.1 mill. by 2101. If the TFR were to increase to 1.9 children per woman, Australia's population would grow to 29.7 mill. by 2051, and to 35.8 mill. by 2101. In both cases the population would continue to grow beyond 2101 (graph 5.27). With a medium fertility assumption of 1.7 children per woman Australia's population would reach 28.2 mill. by 2051 and 30.6 mill. in 2101. If the TFR fell further, to 1.5 children per woman, Australia's population would peak at 26.7 mill. in 2051 before declining gradually to 26.1 mill. in 2101. Under each of these scenarios, fertility being below replacement level (TFR of 2.1), in the future Australia will move from a state of natural increase (an excess of births over deaths) to a state of natural decrease (an excess of deaths over births). However, a state of natural decrease will not necessarily lead to population decline provided that gains in population growth due to net overseas migration offset the loss due to natural decrease. In contrast, if fertility were to increase to replacement level Australia's population would increase to 31.3 mill. by 2051 and 41.7 mill. by 2101, and natural increase would continue beyond the projection period. Since each generation would replace itself, the population would eventually achieve stability in terms of both size and age structure. The level of fertility affects not only population size and growth, but also the age distribution of the population. The impact of fertility is most evident in the younger age groups of the population. Low levels of fertility mean fewer children born each year and, therefore, proportionally fewer people in younger age groups, resulting in an older (or 'topheavy') population. Conversely, high levels of fertility enlarge these groups and result in a younger population. By 2051, the median age of Australia's population could range from 43.1 years to 47.4 years under the high (TFR of 1.9) and low (TFR of 1.5) fertility assumptions respectively. This is considerably older than the median age of 36.4 years in 2004. Should fertility remain at 1.8 children per woman the median age will be 44.2 years by 2051. Replacement level fertility would result in a lower median age of 41.1 years by 2051. 5.28 PROJECTED AGE STRUCTURE, By varying fertility assumptions  June 2051 By 2051, the proportion of the population aged under 15 years could vary from 13% to 17% under the low (TFR of 1.5) and high (TFR of 1.9) fertility scenarios respectively, a lower proportion compared with 2004 (20%). Should fertility remain at 1.8 children per woman, 16% of the population would be aged under 15 years. If fertility were at replacement level (TFR of 2.1), 18% of the population would be under 15 years (graph 5.28 and table 5.29). In 2004 people aged 65 years and over comprised 13% of the total population. By 2051, 25% of the population will be aged 65 years and over under the high fertility assumption (TFR of 1.9), or 27% under the low assumption (TFR of 1.5). If fertility remained at 1.8 children per woman, people aged 65 years and over would account for 25% of the population by 2051. With fertility at replacement level (TFR of 2.1), the proportion of the population aged 65 years and over would be lower at 23% by 2051.
REFERENCE McDonald, Peter 2005, 'Has the Australian Fertility Rate Stopped Falling', People and Place, vol. 13, no. 3. pp.15

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