[tacticalturtle]

This piece seems to do a good job investigating it:

https://jamesgrubman.com/wp-content/uploads/2022/06/2022-06-...

The original source was a study in the 1980s examining 200 family businesses in manufacturing in Illinois, and since then a collection of financial advisors and estate planners have cited it (often without attribution).

Edit: As an aside, I understand that different industries have different standards - but it seems insane to me that any professional piece, let alone a well known brand like Nasdaq, would drop a statistic like that without any kind of attribution.