Terrorist attacks and the male-to-female ratio at birth : the Troubles in Northern Ireland, the Rodney King riots, and the Breivik and Sandy Hook shootings

Abstract

Introduction: Males are usually born in excess of females. The ratio is often expressed as M/F (male divided by total births). A wide variety of factors have been shown to influence M/F. Terrorist attacks reduce M/F. This study was carried out in order to ascertain whether individual terrorist attacks influenced M/F in relevant populations.

Methods: The following events were studied: the Troubles in Northern Ireland, the Los Angeles Riots (the Rodney King affair), the Breivik shooting (Norway), and the Sandy Hook shooting (Connecticut).

Results: Northern Ireland, M/F was significantly lower during the Troubles (1969–1998) than during the period before (p = 0.0006). There was a very sharp dip in 1978 (p ≤ 0.004) during this particular year of renewed violence and heavy civilian attacks. Rodney King riots—late April 1992, M/F dipped significantly in August 1992, 4 months after the riots (p = 0.044). Breivik Shooting—22/07/2011, M/F dipped significantly in December 2011, 5 months after the event (p = 0.004). Sandy Hook Shooting—14/12/2012, M/F dipped significantly in April 2013, 4 months after the event (p = 0.009).

Discussion: M/F dips follow catastrophic or tragic events if these are felt to be momentous enough by a given population. All of the above events caused significant population stress. The M/F dips noted may have been caused by population stress which is known to lead to the culling of frail/small male foetuses. The dips noted are comparable to a substantial proportion of quoted values for perinatal mortality, potentially elevating this a public health issue.