How is that? It seems reasonable to believe, all else being equal, that someone that's been convicted of a crime has committed more crimes than someone that hasn't been convicted.
Why? Being caught committing a crime is less a sign of committing a crime but in doing it in a way that got you caught. Serial committers often go years uncaught... from petty burglars to assaulters.. a lot of people get caught their first time, its the ones who dont get caught that are more dangerous...