Australia has a serious aging problem: our fertility rate is below the level needed just to keep the population steady (namely, 2.1 children per woman). At present fertility rates (1.88 cpw) there will be fewer workers whose incomes will be supporting more people. Immigration may defer the problem but not solve it.

The conditions that determine parents’ decisions are complex, including government benefits, the costs of raising children, social expectations and broad economic circumstances. The wish for children competes with the wish to maintain a certain lifestyle. For couples, present realities and future expectations are powerful determinants of human fertility.

This we share with kangaroos.

The Wikipedia entry on kangaroo reproduction notes: ‘Usually, during a dry period, males will not produce sperm, and females will only conceive if there has been enough rain to produce a large quantity of green.’ The kangaroo, it seems, has a marsupial womb with a view.

Economically, Australians have been going through a ‘dry period’ for some years following the ‘green’ years from 2001 to 2010. Will this affect fertility?

Fertility collapsed in the economically desperate years of the early ‘30s, grew steadily after WW II, peaked at 3.5 cpw in 1961, and began to decline in the recession that began in that year. In 1982 the rate was 1.93 cpw. From then to 2001 the rate declined steadily to 1.72 cpw. From 2000 – 2012 it climbed rapidly to 1.93cpw and stalled. In 2013 it declined to 1.88 cpw.

Explaining these fluctuations is difficult because it is clear that multiple factors — social, cultural and economic — are at work. Nevertheless, we cannot diminish the power of financial ‘dryness’ and drought, and the cost-benefit calculations that men and women make in deciding whether to have children. Correlation does not necessarily show causation; but consider the following.

A 2008 survey by Matthew Gray and others identified 27 factors likely to be of varying importance in the decision of men and women about having children. The factor or condition that was placed first in importance by both women and men was capacity to afford supporting a child.

The rapid increase in fertility between 2001 and 2012 occurred at the same time as real net disposable income per capita rose from around $30,000 pa to around $38,000 pa. Green-flushed men and women hurried to their beds. This was the era of notable prosperity that began to fade with the GFC.

So, we have a picture of correlation between rising per capita purchasing power and higher fertility as the relative costs of children decreased.Determining causation is difficult in the social sciences, including demography, and fertility prediction is therefore risky. Recent policy and circumstances have led to economic sluggishness and stalling of significant progress in disposable incomes for a great many Australians. If these conditions remain or get worse there are likely to be direct implications for fertility.

We have already seen the return of fertility decline from 1.93 cpw in 2012 to 1.88 in 2013. This does not yet represent a trend; but if fertility continues downwards in tandem with economic weakness, the suspicion of a causal relationship between the two will be strengthened, with clear implications for policy in relation to the aging problem.

However, the kangaroos seem to be doing quite well; for them, things are still fairly green.