"Operation Buttondown, the code name for the FBI's campaign to crush the Mafia, reduced the number of families operating in the United States from 24 to only nine, FBI officials said. (CNN, 2004)


To answer your question, I think Pittsburgh is a good example. There are at most a few members still living. Maybe only one. We've seen recent cases, typically revolving gambling, that have involved people that could still be considered associates or relatives of deceased members. There's no functioning hierarchy left, and so not much in the way of coordinated activity you'd see directed by a viable family, but still a handful of guys here and there involved in the rackets.

It would probably be best to compare it to the sun going down. It doesn't suddenlygo from light to dark. Likewise, a family dying off is a gradual process. There's no meeting where the remaining members get together and decide to call it a day.