Because self-report is a valuable and often irreplaceable source of information about emotions, it is important to learn how measurement properties change across different demographic samples. Previous findings of mean differences in the level or variability of trait emotions for men versus women or across ethnic groups suggest that there may be differences in the internal consistency of the same measure when applied to different groups. Research groups using the Differential Emotions Scale (DES) have also begun to use the DES or derivative measures in children as young as 5 years old, raising questions about the psychometric performance of the measure across the life span. The present study uses reliability generalization to synthesize findings from 30 samples of raw data involving a total of 2,407 participants. Results indicate that higher socioeconomic status is associated with increased internal consistency in emotion scales. Age and majority ethnic status also were positively associated with internal consistency on a few emotion scales, whereas gender appeared unrelated to reliability of self-reported emotion.