It shows the sex ratio at birth, whereas the census shows the ratio for children aged 0-6 (census figures for the sex ratio at birth have not been published).

ECONOMIST: Banyan

The other reason specific to a few Asian societies is because a combination of traditional preference for sons and the availability of sex-selective abortion skewed the sex ratio at birth 20 years ago, leaving too few native-born women now.

ECONOMIST: International marriage

The 2005 "mini-census" reported that the sex ratio at birth, expressed as the number of boys per 100 girls, was 119--when the global average was somewhere between 103 to 106.

FORBES