Why has Sweden got more boys than girls?

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There is something odd going on with the ratio between boys and girls in Sweden. The latest estimates suggest there are 123 boys for every 100 girls among 16 and 17-year-olds. That's an even greater imbalance than in the same age group in China.

The natural "sex ratio at birth" is 105 boys for every 100 girls, according to the World Health Organization - and official statistics show that in 2014, there were 108 boys for every 100 girls among Sweden's 16 and 17-year-olds.

But the country now has 123 boys for every 100 girls in this age group, according to Valerie Hudson of Texas A&M University.

If this is correct, it will be quite something. China's one child policy and a preference for sons led some couples to opt for sexually selective abortions, contributing to a sex ratio there of 117 boys for every 100 girls aged 16 and 17.

Hudson's estimate for Sweden was calculated by adding asylum applicants in 2015 to the current population figures - and she is provisionally assuming that all applicants will be granted residency permits. The number of those who actually receive asylum will not appear in official population statistics for another year or so.