Reading through Garry Kasparov’s record of his chess games , I get a bit of a better idea of why Kasparov and others claim that Karpov-Kasparov matches triggered the explosion of analysis and in depth study of various openings. Here is an example that struck me in particular: in game 16 of their 1986 match Kasparov got to the position on the diagram in his analysis and concluded that after 20… b4! the best chance for White is to play is 21. Rb3!
Kasparov – Karpov, 1986 match, analysis position from game 16
Amusingly, this whole line of the Zaitzev variation of the Spanish opening was then re-played 20 years later – in K.Lahno-E.L'Ami, Wijk aan Zee 2006, and probably in some other games. To me that seems to indicate that it takes 10-20 years for the chess world to catch up with Kasparov’s opening preparation from the pre-computer era.
Game 16 of the 1986 match is definitely one of the main highlights of Garry Kasparov on Modern Chess, Part Three: Kasparov v Karpov 1986-1987
Replay through the entire line with brief notes from Kasparov