To the women wishing to have a baby: if you want a boy, try to birth at as early an age as possible and live for a few years in a country where average pay is likely to increase the most during the year preceding pregnancy!
This, purely mathematically, might be the advice regarding births of boys and girls. The topic is actual as, according to calculations by economist Ohto Kanninen and sociologist Aleksi Karhula of Turku University, in OECD nations the link is strongest in Estonia.
The sex ratio at birth (SRB) serves to show how many boys are born per one girl. Usually, it is above one and globally stands at about 1.06 to 1.07. Among other causes, fluctuations are being tied to changes in economic climate.
In their research of 23 OECD nations for 1971–2012, statistic analysis by Finns showed a ling related to growth of income by at least five percent – with every following one percent rise in net income, 0.39 more boys were born per every thousand girls year-on-year.
Overall living standard irrelevant
At that, the authors emphasise that the key word is change of income and not the overall level of income. Otherwise, the Norwegians would only have boys and Romanians birth girls.
Citing Estonia’s rapid wage rise in 1997, 2000 and 2005–2007 with close to ten percent of increase in pay, the authors note the link may be the strongest, the steeper the pay rise.
The link shown by the Finns is actually nothing remarkable and goes to explain the Trivers-Willard hypothesis written in 1973 regarding female mammals able to impact sex of offspring according to prevailing conditions.
The scientists Karhula and Kanninen would strongly stress that caution be applied to interpretation of the results, citing cases of over-interpretation by statisticians.
As also acknowledged by senior analyst at Centar applied research centre Indrek Seppo, according to whom the «result turns statistically insignificant as soon as Estonia is taken out of the data. In Estonia, the link is especially strong but it may be a pure coincidence – this might rather be viewed as an interesting hypothesis than scientific knowledge.»
For the paper by Finns (in English), click here.