Research on generational differences has typically focused on how the current generation is different than those in the past and the implications of such differences for work and non-work outcomes. This research is often based on the assumption that experiences shared by individuals at particular ages and points in time create distinct generational cohorts. However, most studies have only looked at mean differences while ignoring differences in the extent to which variability within the generation represents the shared experiences mechanism and changes in within-generation variability reflecting shared experiences have not been tested. In this paper, we used Bayesian non-parametric modeling techniques to simultaneously model changes in both means and variances over time on a measure commonly used to characterize generations, the Narcissistic Personality Inventory (NPI). Results showed that there were no systematic changes in NPI variances during the last 35 years and some evidence of small, non-linear changes in NPI means. These results differ from previous studies that did not address variability but did find mean generational differences in narcissism, raising questions about those studies as well as about research on generational differences and the methods used to assess change over time.