A whole bunch of games get played with these numbers, largely because they are crunched by people who don’t understand statistics. In which group I emphatically include myself.
Here’s an interesting analysis by a guy who does know the math, and who I trust to use his knowledge honestly.
“The data from the 2008 Bureau of Justice Statistics, ... telling us that five out of six single-offender interracial crimes of violence involve a black perp and a nonblack victim.”
http://www.vdare.com/articles/john-derbyshire-on-uncle-tim-wise-cultural-marxists-can-t-do-math