I was a CFII circa 1970-1975 and I think it started in that time frame. I
never had a BFR before 1975 so maybe it was after 1973. I didn't fly from
1975 to 1998. Sold my Arrow and moved to Southern California. I don't
recall any rash of accidents calling for the change and there was no
significant improvement in accident rate after implementation.

Rod

"