It all got a little controversial when they were running their ill-fated Grand Slam Cup, which was a factor in determining the World Champion. When some top players did not play that as in the case of Stefan Edberg in 1990, the award some felt, went to the wrong player (Lendl).
Roger Federer collecting the ITF trophy
These days with the ATP Tour Finals, it’s still can be confusing. For example, Davydenko won that a few years ago and he certainly was not he best player of the year, so in some ways the World Champion picks themselves.
I imagine Djokovic will be the World Champion this year and even if somehow he was not #1, he clearly has been the best player with 1 Grand Slam to go, so we can only hope the ITF has a good decision making process!
Here’s a list of the ITF World Champions of the last 20 years:
1990: Ivan Lendl
1991: Stefan Edberg
1992: Jim Courier
1993: Pete Sampras
1994: Pete Sampras
1995: Pete Sampras
1996: Pete Sampras
1997: Pete Sampras
1998: Pete Sampras
1999: Andre Agassi
2000: Gustavo Kuerten
2001: Lleyton Hewitt
2002: Lleyton Hewitt
2003: Andy Roddick
2004: Roger Federer
2005: Roger Federer
2006: Roger Federer
2007: Roger Federer
2008: Rafael Nadal
2009: Roger Federer
2010: Rafael Nadal