The incidence of homicide is likely to be higher in areas of
poor economic conditions and low social cohesion.21 A potential
selection bias due to non-matching of the location of residence
did not influence the validity of the major results of this
study, because the results of the conditional logistic regression
analysis did not show an influence of location of residence to
homicide deaths. A potential bias is related to a reporting bias
because controls gave self-reports, while this was obviously
impossible for the murder victims. However, strong relationships
shown between cases and controls in terms of key variables
revealed little effect of this potential bias.