Agreed, if there were a data source that showed the leads for each show for the last 30 years, that would be great.
I just had a thought about removing them from the analysis where their character is 'Ensemble', which would help, but for Charlie, that wouldn't really help as of his seven roles, only one is listed as 'Ensemble', the others are character descriptions, such as 'Angel', 'Addams Ancestor' or 'Telephone Repairman'

IBDB does list the cast in order, so I could use that, but it's then impossible to work out at which point to cut off. I could use the first 1, 2, 4 listed, first x% etc. but it's not an exact science. I might have a play with that though to see what comes out.