Well you just pointed it out, one of the factors one can clearly say Penson was one of the largest. They had 437+ brokers under them only behind Pershing with it’s 800+ brokers making them the second largest clearing service as to the number of brokers they serviced. It is a factor in which one can support such a statement but there is another one relative to here, as each clearing firm specialized in clients and markets for that matter. You cannot compare Pershing to Penson, two completely different cliental involved, Pershing was mostly institutional investment brokers as opposed to Penson with majority retail.
The thing that Penson was known for as being the largest for is the OTC Marketplace, they cleared the majority of OTC marketplace transaction. Not exactly a huge claim in the grand scheme of things, but none the less it was the largest online clearing firm for the OTC.
I agree the degree of their operations does not amount to much when put up against JP Morgan and GS for that matter, but here on Ihub you have to remember almost everything revolves around the OTC and therefore when you say the largest clearing firm it is correct to say Penson as that was the largest clearing firm involved in the OTC.