Do self-reports and informant-ratings measure the same personality constructs?

Personality researchers often supplement or substitute self-reports with ratings from knowledgeable informants, at least implicitly assuming that the same constructs are measured regardless of the source of ratings. However, measurement invariance (MI) of personality constructs across these rating types has rarely been empirically tested. Here, this was done for the Five-Factor Model domains and their 30 facets (N = 3,253). All facets and all domains but Agreeableness met the level of invariance (metric MI) required for comparing the relative standings of individuals across self-reports and informant-ratings, which is what researchers mostly do. However, ten facets and the Agreeableness domain scale failed to achieve the level of invariance (scalar MI) recommended when comparing mean scores. In conclusion, self-reports and informant-ratings appear to measure similar constructs for most research purposes.