Registered Sex Offenders: the "Levels"?

Well, now that we have threads in three different forums about Registered Sex Offenders, may I ask for a simple definition of what constitutes the Levels that are referred to in those threads? I gather it references either predicted likelihood of recidivism or heinousness of original offense, but it’s not clear, and I have no desire to go Googling for sex offender information – I can imagine the results! It might also be useful to get a paraphrase interpretation of how they work, rather than the classic legalese that I presume they’re written in.

A request to members: This is a request for factual data as is the purpose of GQ. If you want to debate or rant about the idea of such classifications, the idea of registering sex offenders, or the idea of allowing them to live among the general public, please do it in one of the appropriate forums. Thanks.

I was interested in the subject too but I couldn’t find anything concrete

http://www.mass.gov/sorb/levels.htm

It just seems to say (in Massachusetts at least) it is just up to the registry board to determine how high the recidivism rate is and that determines the level. It doesn’t seem to talk about how many crimes there were, the nature of the crimes, or anything like that.

From here:

No doubt the particular criteria vary from state to state. The above is for New York State.