Identity boundaries hold stable for only about fifty years.

Evidence

The longer the period and the wider the geographical space taken into account the more difficult this becomes. Collective identities are stable enough to generate clear boundaries of difference only over brief periods. The mosaic of difference seems stable enough only in, say, 50-year segments. Some differences may seem to be of longer duration, but if we examine them closely it turns out that over time their meaning or function changes radically, so that continuity is a superficial impression only. — David Theo Goldberg, John Solomos, A Companion to Racial and Ethnic Studies, 184

Categorization

• QUESTION: The claimed ~50-year stability span seems suspiciously precise and methodologically ungrounded — worth chasing whether this is assertion or supported finding.
• XREF: Echoes the time-periodization approach in the Frankfurt School material about how Nazism-era continuity claims misread the surface stability of meaning.
• corroborated: 2 independent passages support this claim — David Theo Goldberg, John Solomos, A Companion to Racial and Ethnic Studies, 184