Pre-2011, it's 13-6 to Federer.What was the H2H in 2011 and since then?
From 2011, it's 21-10 to Djokovic.
Clearly this swing has something to do with age, but seeing as Djokovic fans do not recognise the concept of age, then we must search for some other explanation, such as voodoo or astrology or blind chance. Take your pick.
Note, though, that they played 19 times pre-2011 and 31 times from 2011.
And still Djokovic only leads the H2H by 4 matches.