International evidence on obesity increases: legal systems and motor vehicle dependence

We find a significant positive link between motor vehicle ownership and obesity in industrialized countries. Surprisingly this association holds for countries with a common law tradition but not for those based on civil law. These relations hold whether we examine trend data, simple correlations, cross-section regression analysis, or panel data regressions. An increase of 100 motor vehicles per thousand residents is associated with a six percentage point increase in obesity in Common Law countries but not in Civil Law countries. The robustness of this main result and the clear link between increased ownership of motor vehicles and reduced physical activity suggests the association is causal. Motor vehicle dependence is an important link in the growth of obesity in countries with a tradition of common law where individual liberty is encouraged; the link is statistically non-existent in countries with a civil law background where the rights of the individual tend to be circumscribed by the power of the state. This suggests that efforts to discourage the over-reliance on the automobile would have the greatest obesity reducing impact precisely in those countries where it is most difficult, in terms of legal heritage, to implement such measures.