Steven Levitt and Mark Duggan wrote a paper using statistical analysis to look at match rigging in sumo wrestling. Levitt also wrote about this paper in the book Freakonomics. In a new Sports Illustrated report, 150 matches are being investigated by tennis officials. Here is an excerpt of what Steven Levitt has to say about rigging tennis matches:

My hunch, having seen no data and only read this article, is that the number of rigged tennis matches will ultimately turn out to be very small. My reason for this conclusion is that there is something absent from tennis that is present in sumo wrestling: a highly non-linear incentive scheme. The eighth win in a sumo tournament is worth far more than a six, a seventh, a ninth, or a tenth win. As such, the sumo wrestlers themselves can see strong gains from trade. In tennis, however, the only apparent incentive at work is bribes related to gambling. … The lack of incentive for tennis players to trade wins has to mean that endemic cheating is far less likely. The fact that betting markets are small — especially on unimportant matches– also makes it more difficult to cheat, because big bets will stick out like a sore thumb. In key matches, the prize money stakes are so high that rigging is unlikely.

In fact, I would be willing to bet that steroids are much more common in tennis than match rigging.