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New Zealand is in the middle of a baby boom

Increases in the number of births in New Zealand often result in headlines proclaiming the arrival of a 'baby boom', but is this valid?

Baby boom is a phrase commonly used by demographers to describe the large numbers of people born in the period following World War II. As such, it describes an historical period more than a demographic phenomenon. However, that won't help us answer the current question. So, for argument's sake, let's define a baby boom as 'a significant increase in the birth rate.'

For instance, 64,540 births were recorded in 2008, a number surpassed only by historical highs in the early 1960s. However, a high number of births does not necessarily mean a high birth rate. The birth rate depends on the size of the population producing the births, and this has grown substantially over the last four decades. The total fertility rate for 2008 was 2.2 births per woman. Although this was the highest rate since 1977, it is still only 0.2 of a baby higher than the average birth rate for the last 20 years (2.0 births per woman).

In 1961, the birth rate was around 4.3 births per woman. The number of births registered in the December year was 65,390 – the highest ever registered. In the last 50 years, the female population has increased by around 1 million. If the 1961 birth rates applied today we would have had around 112,000 births in 2011. In fact we had only 61,400. With the current birth rate only just reaching replacement level (2.1) we cannot justify the claim that New Zealand is having a baby boom.

Conclusion

This myth is busted.

How did this myth arise?

The birth rate has been very stable over the last couple of decades, fluctuating around 2 births per woman, with a high of 2.2 in 1990 and 2008, and a low of 1.9 in 2002. This period of stability may overemphasise the ups and downs. In contrast, the period from 1968 to 1987 saw a significant decline in the birth rate – from 3.3 births in 1968 to 1.9 in the early 1980s.

What is replacement level fertility?

Replacement level fertility is the average number of children a woman needs to have to produce one daughter who survives to childbearing age. It is also described as the total fertility rate required for the population to replace itself, without migration. The internationally accepted replacement level is 2.1 births per woman. It allows for the mortality of females between birth and childbearing and the birth of more boys than girls. On average, throughout the world, 105 boys are born for every 100 girls.

For your information

Births and Deaths – information releases 
Statistics on the number of births and deaths registered in New Zealand, and selected fertility and mortality indices. Updated quarterly.

Published 22 June 2012, based on information previously published on 17 December 2007.

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