Sex bias in data collection refers to the underreporting or misreporting of demographic, social or economic characteristics associated with one of the sexes. Some examples of sex bias in data collected are: underreporting of women’s economic activity; undercounting of girls, their births or their deaths; or underreporting of violence against women.
United Nations Statistics Division – UNSD. Glossary on Gender Statistics –
Global Gender Statistics Programme. Available at: http://unstats.un.org/unsd/genderstatmanual/Glossary.ashx