With all due respect to Garry Kasparov, it's probably Ken Rogoff. The Financial Times weekend edition has Rogoff featured in its "Lunch with the FT" column, which is always an entertaining read. (You may have to register at the site to read it.) ChessBase news also has done stories on Rogoff, most recently in December at the London Chess Classic.
Interesting to note that it's the retired GMs that are most influential in the world, but then again the active ones have to play chess for a living.