30 December 2020

Human sex ratio in Ancestry's 1911 Census

According to Wikipedia "the natural ratio between males and females at birth is slightly biased towards the male sex, being estimated to be about 1.05[2] or 1.06[3] or within a narrow range from 1.03 to 1.06[4] males/per female born."

The latest UK data shows males outnumbering females, a ratio 1.05, until age 54 — https://www.indexmundi.com/united_kingdom/sex_ratio.html/. The same is true for Canada and the USA.

Birth YearSex Ratio

So it was a bit of a surprise to find the data in the table above calculated from the 1911 census for England, as supplied by Ancestry, showing more females than males except for 1910. The stats are for births in +/- 10-year intervals around the decadal year. 1905 is for +/- 5 years, 1909 and 1910 for just that year.

As men have a shorter lifespan the predominance of older women and the trend toward equality in numbers for younger people isn't surprising. But why the much larger proportion of women?

Could it be that men have emigrated in larger numbers? Could it be they were overseas on military service? Or could it be there's a problem with the assignment of gender? 

This extract from a randomly selected census form shows there was a lot of confusion in completing the return. 

As neither Findmypast nor MyHeritage nor FamilySearch has the capability to compute statistics for 1911 by gender it's likely a tacit recognition the derived stats are not to be trusted.

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