Friday, October 26, 2012

Older mums - everything old is new again

Behind the misleading headline

A record 12,800 babies were born to women over forty last year, up from 7100 a decade earlier. But - while recent - the trend to late births isn’t new.

Australian National University demographer Peter McDonald says late births were far more common in the nineteenth century. “Back then a lot of women had more than ten births. They were continually giving birth every two years until well into their forties” he told the Herald.

“Towards the end of the nineteenth century they started to control their births, stopping after a certain number of children.”

“Older births began to grow again about a decade ago, primarily because women had postponing having their first child, which delayed subsequent births. In vitro fertilization has also boosted late births.”

Professor McDonald thinks the drift to later births will soon slow, and the Bureau of Statistics report bears this out. Although the proportion of late births continued to climb last year, the typical age of mothers giving birth fell.

He thinks the paradox is explained by a change in women’s behaviour in the mid-2000s. Instead of delaying births some brought them forward in response to publicity about about the dangers waiting, and perhaps the introduction of baby bonus. Women now typically start at 28 years and 11 months instead of 29 years and four months. In time those decisions will result in fewer women having their later children after forty...

The figures show the government’s decision to cut the baby bonus for second and later children will hit most women giving birth. Around 56 per cent of babies born last year were second or subsequent births. “Most Australian children grow up in families with three or more children,” Professor McDonald said.

In today's  Sydney Morning Herald

The Crunch Data Blog

Peter Martin takes a look into birth statistics and what they tell us about the baby bonus.

They're fair questions. How many babies born last year were first children? And how many were second or later children? We went after the answer with Thursday's release of the ABS births numbers because it would have given us a handle on the number of births who would get the lower $3000 baby bonus announced in the mini-budget for later children instead of the previous $5000.

The ABS hides a "sort of" answer in the "Explanatory Notes" page of its web release. It's Note 51. The proportion of last year's babies who were first children was 43.8%, meaning most of the babies were second or subsequent children. (By the way 1.3 per cent of the babies joined five or more sisters or brothers)

Its a "sort-of answer" because it "excludes births registered in Victoria, Queensland and Tasmania". That's because those states don't collect information on how many previous babies the mother has had, only how many the father has had (including those in earlier relationships).

Given that it is the mother who has the children, the Victorian, Queensland and Tasmanian idea of what constitutes a second or a third seems strange (and certainly won't be used by the government in deciding what size baby bonus to grant).

Will they change it? Probably not? Is the ABS stuck with what it gets from the births deaths and marriages registries? Probably.

But wait. ANU demographer Peter McDonald says the Australian Institute of Health and Welfare has a much better data set it complies at the hospitals from nurses and midwives who actually ask each new mother how many children she has previously had. But it's late. The most recent publication is for 2009. It's also a magnificent source of data, far better than the ABS publication. It details the length of stay in hospital, everything - even the most popular month for births, which is October.

In The Crunch Data Blog

Related Posts

. 2008. We had a baby boom

. A boosted baby bonus means...bigger babies. No kidding.

. Births, conceptions and deaths - Money changes everything