Researchers generally recognize that racial identification may shift over the life course. However, there is less consensus about the prevalence of these shifts. Previous estimates suggest as many as 6% of Americans shift their racial identity. Using administrative data on Social Security applications from 1984 to 2007, we quantify the magnitude and direction of shifts in racial and ethnic self-identification among Black, White, Asian, American Indian, and Hispanic members of the “Greatest Generation,” those born between 1901 and 1927 (N = 410,388). Approximately 9,274 (2.3%) persons in this dataset changed their racial or Hispanic identity, with distinct patterns of change for racial-ethnic subgroups. Overall, the most common shift was from a non-White identity to a non-Hispanic White identity. We then link to the 1940 Census to investigate whether social status in youth and young adulthood predicts a shift in identity in later life, and we find a positive and significant association between socioeconomic status in early life and a shift from non-White to non-Hispanic White identity. These systematic patterns would be unlikely if these shifts were due entirely to measurement error. We conclude the prevalence of racial fluidity is itself contingent, varying across time and cohort with response to racial climate, events in greater society, and social position.