Let's look at "Sex Offenses and Offenders", and aim high: in 1994 6% of 900k state prisoners were in for something that would incorporate that designation.
Not good enough, though a current version of that number would help set a lower limit.
I don't understand why the statistics that I want are so hard to find. With all the data they collect, the DOJ statisticians should be able to come up with numbers that provide some answer to the question, "How afraid of strangers should I be?"