Freakonomics (July)

I am reading Freakonomics along with Dark Tide this summer. One thing I question is how are the authors, Dubner and Levitt, finding this information and then how, in their minds, do any of these things correlate? Another question I have is why these particular topics? What gave them the inspiration to talk about how sumo wrestlers and teachers are alike? And by the answer they gave in the book (they both cheat) you could, logically, say that any two people, professions, or groups are alike because almost everyone cheats. Furthermore where would one go to find information on sumo wrestlers and how they cheat? The book cites scores from every official sumo match (which I'm assuming you could find as easily as you could find the Red Sox scores). But how is it the authors can take the gigantic jump from sumo wrestlers to teachers? In what way do these two things correlate? Not only the sumo wrestlers and teachers but things like real-estate agents and the KKK! How could they possibly go from something that is so common and seemingly harmless as a real estate agent to the white supremacist group that rampaged the country and struck fear into the large majority of African Americans? Maybe it's just the fact that there is something to compare and one little thing that makes them similar that makes them a great comparison. Or maybe it's just that the authors really do want to show the hidden side of everything and so finding two things that seem vastly different and finding one common factor is finding "the hidden side of everything".