Wonder what it is if they tallied the illegal immigrants in with that. Some police forces will not charge someone who is suspected of being here illegally. They cannot ask and don't want to open a can of worms.
Since there is not even an arrest made, no charge goes on the books.
Ironically, a recent story from California claims DUI checkpoints are being used to target illegals:
http://abclocal.go.com/kabc/story?section=news/local/los_angeles&id=7861983