What are other-rated scales composed of? Sources of measurement error and true trait variance in other-ratings of the Big Five

•Other-ratings consist of true trait variance (TTV) and measurement error (raters, scales, items, occasions, randomness).•Available meta-analytical data on Big Five other-ratings were analyzed.•Big Five other-ratings showed relatively little TTV (0-13%).•Accounting for low inter-rater reliability and convergent validity of Big Five measures, TTV levels rose somewhat (4-26%).•Findings provide important insights on what Big Five other-ratings are composed of.

Other-ratings of targets' traits may consist - besides true trait variance (TTV) - of different measurement error sources, particularly due to raters, scales, items, measurement times, and random fluctuations. Using Gnambs' (2015) and Ones, Wiernik, Wilmot, and Kostal's (2016) procedures for partitioning variance in scales due to measurement error, available meta-analytical data on Big Five other-ratings were analyzed. They showed relatively little TTV (0-13%), which was especially decreased by both low inter-rater reliability and convergent validity of Big Five measures. Accounting for both, TTV levels rose, but were still small to medium (4-26%). These findings provide important insights on what Big Five other-ratings are composed of and how such scale scores may be interpreted and treated in further analyses (e.g., trait-outcome relations).