The Question and Answer section for Freakonomics is a great resource to ask questions, find answers, and discuss the novel.
From the text:
“A regression analysis can demonstrate correlation, but it doesn’t prove cause. After all, there are several ways in which two variables can be correlated. X can cause Y; Y can cause X; or it may be that some other factor is causing...
By the end of it all, 23 wrestlers in total were judged guilty of match-fixing and all were expelled.