McCartney claims the below songs were collaborations. 50/50 more or less! They are quite big Lennon songs, which he is claiming a lot of credit on. Maybe this is perfectly justified also. I am sure there are more examples!
In My Life
Lucy In The Sky With Diamonds ( not sure of the percentage on Lucy)
If I fell ( not sure of percentage buts says co-witten )
The Benefit Of Mr Kite
Should we add the above to McCartneys huge catolog of hits if they are as much his as Lennons ? Not really as he also classes them as Lennon/Beatle songs otherwise he would sing them live - still they are big claims on some of Lennons best works from various 'Beatle periods!'......Even on songs like "Help" another 'big' Lennon song he claims something like 30%!!! Quite a few like that I'm not saying he is claiming too much credit just pointing out some interesting insights.