Is use of the general system justification scale across countries justified? Testing its measurement equivalence.

System justification is a widely researched topic in social and political psychology. One major measurement instrument in system justification research is the General System Justification Scale (G-SJS). This scale has been used, among others, for comparisons across social groups in different countries. Such comparisons rely on the assumption that the scale is measurement equivalent. However, this assumption has never been comprehensively tested. Thus, the present two studies assessed the measurement equivalence of the G-SJS following classic measurement equivalence guidelines (i.e., multigroup confirmatory factor analyses) in Study 1 and using a new method for comparing larger numbers of groups in Study 2 (i.e., alignment optimization). In Study 1, we analysed the measurement equivalence in Great Britain (n = 444), Germany (n = 454), and France (n = 463). In Study 2, we used a publicly available dataset consisting of 66 samples from 30 countries (N = 13,495) to again assess the measurement equivalence of the scale. Results indicated (partial) metric equivalence, but not scalar equivalence in both studies. Overall, the studies indicate that mean comparisons across the examined countries are not warranted with the current form of the G-SJS. The scale needs to be revised for valid cross-country comparisons of means.