For over 20 years, the Defining Issues Test (DIT) has used the P index. In view of criticisms, a search has been underway for a new index. The authors propose a working definition of construct validity, systematically reanalyze existing data sets ("classic" studies) with new indexes, and make comparisons to trends obtained using the P index. The criteria for construct validity are (a) sensitivity to educational interventions, (b) differentiation of age-educational groups, (c) upward movement in longitudinal studies, (d) correlations with moral comprehension, (e) correlations with prosocial behavior, and (f) correlations with civil libertarian attitudes. As meta-analysis demonstrates, a new index, N2, generally outperforms the P index.