Are stepmothers evil or simply unskilled? Infant death clustering in recomposed families

We measure the concentration of infant deaths in families in the historical populations of Krummhörn, Germany and Québec, Canada in order to investigate whether mothers in recomposed families differ regarding their maternal quality. In particular, we are interested in whether stepmothers in Krummhörn are responsible for a diminution in the survival of their stepchildren because they poorly substitute maternal child care or because they disadvantage their stepchildren. The concentrations of infant deaths within the two populations are measured with Lorenz curves and Gini coefficients, and are compared with expected concentrations given by draws from a binomial distribution. Alleged differences between actual and calculated concentrations represent "causal" death clustering. In the Krummhörn region there is little evidence for "causal" death clustering that would indicate variations regarding their maternal quality, whereas Québec mothers exhibit a distinctively higher concentration of infant deaths.