It's interesting that you brought that up, since I had just read this article: http://www.washingtonpost.com/news/post-nation/wp/2014/09/08/how-many-police-shootings-a-year-no-one-knows/
I used to be quicker to state the whole rarity argument, that most officers will never even fire their gun in the line of duty over their entire career. Part of me still thinks that the advent of technology is holding officers more accountable than in the past, since we have so many different ways to track what they are doing on the job.
But there really isn't any reason for us not to have the hard facts as to how many police shootings there are in a year. That should be something the State and Federal government is completely on top of, and they are clearly failing us here. How can we even fully understand the problem without the data?
So write your congressman and get him or her to push a mandate forward to collect this data. Then we can tackle how to lower these tragic situations using real information.
The article only speaks of shootings I would actually like to have them track any use of "justifiable force" in an arrest as some of those end up with a man cuffed and an officer breaking his limbs.