This is probably a good thing. A large prize might create some rather perverse incentives for, uhh, direct intervention in the data set.
Blech. This is not an easy problem and that's all they offer? <snarky>Is that the dollar value Philly puts on a life?</snarky>
Not understanding the downvotes. Solving this problem would easily save hundreds of thousands of dollars, if not millions, in law enforcement and litigation costs. To put a paltry $100 reward for _preventing murder_ is, frankly, pathetic.
The prize isn't for preventing murder; it's for predicting murder. There are significant practical differences, particularly with respect to the incentives created.
Being able to predict where/when murder happens leads to a more efficient and effective distribution of law enforcement. Other cities have done this with non-violent crime/traffic violations/etc., and crime has gone down. So prediction = prevention.
In fact, if your submission helps prevent murders, you would tend to lose the contest.
Well, predicting murders would cause a re-allocation of the police department's resources, arguably preventing some of those murders.