"So when you look at the report you just disregard nonreportable positions?"
Yep.
"I guess I am somewhat confused by the fact that there are about twice more nonreportable long positions than short positions on SP500 (I thought these numbers should be about equal). And how do we know whether these "extra" long positions belong to commercials or to non-commercials?"
We don't, and my best advice is, don't worry about it. I've tried several times to figure out how all the numbers on those reports add up, but all I accomplished was giving myself a headache. All we know for sure about the non-reportable positions is that they are small enough so the Commission doesn't make the traders report them.
The only thing you need to look at is, are the commercials net longer or net shorter this week than last week? This is just one piece of a large puzzle, i.e., market sentiment in general. Don't try to make more of it than what it is, or you'll get drain bamage. {G}
(:
augie