I was interested to read this New Zealand Herald article this week:
We've all heard the jokes about how lockdown leads to a "baby boom" - but it turns out being stuck at home does lead to a rise in birth rates.
New information from Stats NZ for the year ending in September 2021 confirms an increase in live births compared to the same time last year.
The data reveals there were 59,382 live births registered in Aotearoa, an increase from 57,753 last year.
And the fertility rate has risen slightly as well, sitting at 1.66 births per woman, up from 1.63 at the same time in 2020...
Significantly, the number of live births as at September 2021 is the highest since 2015 - long before the pandemic changed all of our lives and lockdown was the last thing on anyone's mind.
This was a little bit of a surprise, as the recent births data has shortly historically low birth rates in New Zealand. So, a 'baby boom' would come as a surprise. However, when we actually look at the data, we find that calling it a 'boom' is a mischaracterisation. Here's the data on the raw number of births by quarter in New Zealand, from 1991 to 2021 [*]:
The number of births per quarter fluctuates between about 13,500 and 16,500. There was a bit of a downward trend from 1991 to 2003, then an uptick, before the downward trend resumed from about 2009. You can see the recent rise in births at the end of the series. Indeed, the number of births is at its highest level since 2015. You might even convince yourself that this constitutes a 'baby boom'. However, then you'd also need to believe there was a boom from 2007 to 2011, where the number of births per quarter was mostly at or above the number in Q3 of 2021.
There is a problem with looking at the raw number of births though, and that is that it doesn't account for the size of the population. Population has grown a lot over the 30-year timespan shown in the graph above. To account for that, I calculated the number of births per 100 women aged 15-49 years (you can call this the period fertility rate; I use the rate per 100 women, because that makes the numbers a bit easier to interpret). [**] Here's the result for New Zealand as a whole, since 1996:
The trends are somewhat similar to the previous graph, although the overall downward trend is much more obvious. The recent increase in the birth rate is still apparent, but by itself there isn't much to suggest a 'baby boom', maybe just a slight reversal of the recent trend. As you can see, the rate is lower than it was in 2017, and for basically the entire period prior to 2013. It remains to be seen whether the increase in birth rate in Q3 of 2021 is a brief spasm in the data (similar to Q2 of 2015), or the start of a change in fertility trends. My intuition is that it is the former.
So, was this increase in births caused by lockdown? It is easy to speculate that it is, given the timing. However, we can do a little better than that. Auckland has suffered from longer periods of lockdown than the rest of the country. So, if there is a baby boom driven by lockdowns, it's likely that it would be more apparent for Auckland than for the rest of the country. That isn't what we see though. Here's the birth rates for Auckland over the period since 1996:
That doesn't look much different to New Zealand as a whole (which isn't a surprise - more than a third of the New Zealand total is contributed by Auckland). Also, if we compare the change in the birth rate across regions between Q3 of 2019 and Q3 of 2021 (I chose 2019 for the comparison, since it is the most recent year with no effect of coronavirus or lockdowns), we see this:
The biggest increase in the birth rate between 2019 and 2021 has been in the Tasman and Gisborne regions. Auckland barely features at all. The birth rate in Q3 of 2021 is actually lower in Wellington and the West Coast than it was in Q3 of 2019. It's hard to make a case that lockdowns are a cause for the increase in births, unless you can somehow make the case that the lockdowns had a bigger effect in Tasman and Gisborne, and smaller in Wellington and the West Coast (or, you can show that there is some other socio-demographic or economic effects that are able to explain the cross-region differences that seem to more than offset any impact of lockdowns). Now, you could argue that the biggest difference in the effects of lockdown between Auckland and the rest of the country is actually happening now, and so the regional differences in the effect of lockdowns should become apparent in the births data for Q1 of 2022. I guess we will wait and see for that.
So, while there has certainly been an increase in births, it is hardly a 'baby boom' (unless you have an extraordinarily liberal interpretation of what constitutes a boom). And, it is hard to make a case that it was caused by lockdown (unless lockdown and other socio-demographic or economic changes affected birth rates in different regions in some idiosyncratic way, such that Auckland ended up having a very low increase in the birth rate).
*****
[*] The data come from Statistics New Zealand, Infoshare.
[**] The calculations here are based on the births data from Infoshare, plus subnational population estimates for each region, from NZ.Stat. As the data are only provided for 30 June of each year (and only since 1996), I take the 30 June population as the denominator for the rates for Q3 of each year, and use a linear interpolation between each Q3 value to obtain population estimates for the other quarters.
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