The male to female ratio at birth following the Scottish Independence Referendum, September 2014

Abstract

Human male live births exceed female live births by approximately 3%. This sex ratio is conventionally expressed as M/F (male divided by total live births). Many factors have been implicated as influencing this ratio, such as stress. This phenomenon occurred following the Quebec sovereignty referendum of 1995. This study was carried out in order to ascertain whether the Scottish referendum of September 2014 had any effect on the M/F ratio in Scotland. Monthly live births by gender for Scotland were obtained from Scottish Office of National Records for the period January 2004 to July 2015. They were analysed for any significant period changes as witnessed in Quebec in 1995. There were 661166 total births (338850 male and 322316 female births), with an overall M/F of 0.5125 (95% CI: 0.5113-0.5137). There were no changes in M/F in the first five months after the referendum. However, there was a non-significant rise in M/F toward the end of 2014 which continued during much of 2015. The rise in M/F reached its peak in May-June 2015, 8-9 months after the referendum (M/F 0.5199 compared to M/F of 0.5124 for aggregated May-June values 2004-14). There was no significant drop in M/F in the Scottish population in relation to the Scottish referendum. This may be due to a type 2 error since this study was less powered (12 times smaller) than the Quebec study. The non-significant rise may have potentially been caused by increased coital rates as observed after the birth of Prince William in 1982 and for Hong Kong in relation to Dragon years. It will be interesting to analyse the rest of the UK data when this becomes officially available.