In contrast with the plethora of studies concerning the social inequalities in health that have been conducted since the 1980s, there are relatively few related to injuries.^1,2 There are even fewer studies comparing the influence of these inequalities in different countries. So, the publication of Borrell et al’s study on social inequalities in transportation injury mortality across European countries³ is most welcome and timely [see page 138]. Their study elucidated the effect of differing national contexts on the influence of social disparities on road traffic injury (RTI) mortality.

In this commentary, we will first explain what a so-called “contextual effect” is and then illustrate that many such effects can be discovered only through international comparisons. We contend that “dissimilarities” may provide more useful information than “similarities”. Because the contextual determinants of social inequality in RTI mortality between and within countries are different, they have different implications for injury prevention.

WHAT IS A CONTEXTUAL EFFECT?

In linguistics, context refers to the text surrounding a word, giving a better understanding of what the word means. In art, contextualism refers to the way a work of art may only be understood by knowing the historical, political, or cultural circumstances when it was produced. In health research, context similarly refers to the wider situation surrounding the association between an exposure and outcome and how this wider situation may confer meaning on that association.⁴

The study of the effects of collective or …