old joke
KKK has 100 members
in reality though, its 5 members and 95 informants
By the time Reagan became president some 16 years later, they discovered the dues of the FBI infiltrators was the one and only thing keeping the KKK afloat. They discussed ending the program, but thought it would be too risky politically. So it limped along for another decade or so until it was quietly dropped under the Clinton administration.
I would suppose by that time, the ratio was pretty close to what your old joke suggested.