I think, in this case and discussion, it's just about the scale of the influence and power. So yes, if you want to measure the influence and the power of the american mob to the US economy: sum it up and don't distinguish between different groups.
I agree on the scale, but then you really need to put a table comparing with other countries. What happens if I say Italians eat 100 M tonnes of ice scream per year? Is it a lot? A lot compared to what?
I don't agree on the influence and power and that's exactly the point. If you sum up all the US criminals, you get a raw index of criminality in the country, not how much power few criminals have over US people. If all US criminals where part of the same organization, the infamous US mob, that would be a huge problem then. But US mob does not exist, the same as Mafia does not rule all criminality in Italy.
