Wednesday, June 13, 2012

How big is the "Dragon baby" boom?

A "Dragon baby" is a child born under the Dragon sign of the Chinese Zodiac. Arriving every 12 years, the Dragon year is considered auspicious by many Chinese, and children born that year are believed to be blessed with strength and luck. The New York Times reports that mainland Chinese flock to Hong Kong to escape China's one-child policy, and have Dragon children in Hong Kong. 

This birth spike is not without its problems. BBC News highlights that this creates problems as schools and hospitals are strained to accommodate the birth spike. With fewer places in hospitals, schools and jobs to go around, Dragon children look to face a lifetime of intense competition. Given this, surely some parents would opt to avoid the Dragon year. Is this enough to offset the birth spike?

To measure the Dragon birth effect in Singapore, I obtained data on the number of births from 1997. Since the Dragon year is a Chinese belief, I looked at Chinese and non-Chinese births separately. From the graph below, it does appear that Chinese births (blue line) spiked in 2000 which was a Dragon year. The number of Chinese births stood at about 10.3% higher than the preceding year, so is this the Dragon baby effect?

Note: data for 2001 unavailable, and was extrapolated from 2000 and 2002.
Source: Dept of Statistics

No. Other events might have caused birth rates to increase - for example, the region was coming out of the financial crisis, and people were more confident about the future.

As a result, we need a reasonable baseline to compare Chinese births against. Since year-to-year changes in Chinese and non-Chinese births tend to move together (80% correlation), it makes sense to use the number of non-Chinese births for the baseline. This is typically known as the "control group" in research.

[Addendum: in contrast, this article did not use a control group]

Between 2000 and 1999, non-Chinese births grew by 4.6%. Subtracting this from the 10.3% increase in Chinese births, the Dragon effect can then be said to be about 5.7%. This quick calculation corresponds quite closely to the 5% increase in births China authorities were expecting in 2012, another Dragon year. 

At the end of the day, this number is not just a matter of intellectual curiosity, because hospitals and schools need to know how much they need to expand to cater to the birth spike. Without a proper forecast, capacity might increase by too much, or too little.

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