I also remember seeing several references such as "in the year 1957, White scored 55% of all the points in Grandmaster tournaments".
This is interesting because a winning ratio of 55:45 is equivalent to a USCF rating difference of 40 points, and a ratio of 2:1 is about 125 rating points, and so on.
To phrase this differently, if the estimates of money odds are correct, when you sit down to play somebody whose rating is 250 or so points higher than yours, it's just like giving Knight odds to a player of equal strength!
Another way of looking at this is that when you sit down to play Kasparov, he already has a material advantage at the start of the game because his Pawns are stronger than yours (and his Rooks, and his Knights, and so on).
If differences in material can be translated into rating points, this has implications for the theory of piece values.