Economic stress or random variation Revisiting German reunification as a natural experiment to investigate the effect of economic contraction on sex ratios at birthReport as inadecuate

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Environmental Health

, 13:117

First Online: 22 December 2014Received: 04 September 2013Accepted: 04 December 2014DOI: 10.1186-1476-069X-13-117

Cite this article as: Schnettler, S. & Klüsener, S. Environ Health 2014 13: 117. doi:10.1186-1476-069X-13-117


BackgroundThe economic stress hypothesis ESH predicts decreases in the sex ratio at birth SRB following economic decline. However, as many factors influence the SRB, this hypothesis is difficult to test empirically. Thus, researchers make use of quasi-experiments such as German reunification: The economy in East, but not in West Germany, underwent a rapid decline in 1991. A co-occurrence of a decline in the East German SRB in 1991 has been interpreted by some as support for the ESH. However, another explanation might be that the low SRB in 1991 stems from increased random variation in the East German SRB due to a drastically reduced number of births during the crisis. We look into this alternative random variation hypothesis RVH by re-examining the German case with more detailed data.

MethodsOur analysis has two parts. First, using aggregate-level birth register data for all births in the period between 1946 and 2011, we plot the quantum and variance of the SRB and the number of births and unemployment rates, separately for East and West Germany, and conduct a time series analysis on the East German SRB over time. Second, we model the odds for a male birth at the individual level in a multiple logistic regression 1991–2010, ~13.9 million births. Explanatory variables are related to the level of the individual birth, the mother of the child born, and the regional economic context.

ResultsThe aggregate-level analysis reveals a higher degree of variation of the SRB in East Germany. Deviations from the time trend occur in several years, seemingly unrelated to economic development, and the deviation in 1991 is not statistically significant. The individual-level analysis confirms that the 1991-drop in the East German SRB cannot directly be attributed to economic development and that there is no statistically significant effect of economic development on sex determination in East or West Germany.

ConclusionOutcomes support the RVH but not the ESH. Furthermore, our results speak against a statistically significant effect of the reunification event itself on the East German SRB. We discuss the relative importance of behavioral and physiological responses to macro-level stressors, a distinction that may help integrate previously mixed findings.

KeywordsSex ratio at birth Economic decline Unemployment Economic stress German reunification Natural experiment AbbreviationsARCHAutoregressive conditional heteroskedasticity

ARMAAutoregressive moving average

ESHEconomic stress hypothesis

RVHRandom variation hypothesis

SRBSex ratio at birth.

Electronic supplementary materialThe online version of this article doi:10.1186-1476-069X-13-117 contains supplementary material, which is available to authorized users.

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Author: Sebastian Schnettler - Sebastian Klüsener


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