At the link below you will find an analysis of Goldman's prop trading numbers for 2008 (not a good year), using the public records of its charitable Goldman Sachs Foundation. Thanks to a reader for sending this. I don't know how reliable this method is -- it all depends on whether GSF's records reflect the firm's overall trading pattern.
Zerohedge: ... Sometimes no capital is allocated to excluded strategies, but usually, and especially for product agnostic funds such as Goldman, each entity will be allowed its pro rata share based on the "fungible" capital that makes up the firm's entire Assets Under Management. Therefore, the GS Foundation ("GSF"), with its $270 million of capital at the beginning of 2008, would likely get its pro rata allocation as a percentage of the total capital backing the Goldman hedge fund (which can come from such places as Goldman Sachs Asset Management, and Goldman Sachs & Co., which in turn gets it funding via such taxpayer conduits as the Fed's repo operations and the Discount Window). So if Goldman for example had access to total capital of $50 billion last year (roughly), each trade, when allocated to GSF, would account for about half a percent (0.5%), absent special treatment, of the total capital invested or disposed. As an example, if Goldman were to trade $100 million notional in 10 year Index Swaps, GSF would thus be allocated about $500,000 of the trade.
Why is all this relevant?
Were one to comb through GSF's tax filings, one would uncover in 2007 over 500 pages worth of single-spaced trades, and over 200 in 2008, across absolutely every single asset class: equities, indices, futures, fixed income, currencies, credit swaps, IR swaps, FX, private equity, hedge fund investment, you name it (oddly absent are CDS trades). And this is in 2007 alone. These are a one-for-one proxy of absolutely every single trade that Goldman executed in its capacity as a prop trader in the last two years. The only question is what is the proration multiple to determine what the appropriate P&L for the entire firm would have been based on any one single trade allocated to GSF, and subsequently, disclosed in the foundation's tax forms.
... Yet what is obvious no matter how the data set is sliced and diced, is that the firm was bleeding money across virtually all prop-traded groups in 2008. Is it any wonder that the firm's only source of revenue is courtesy of i) the near-vertical treasury curve (thank you taxpayers) and ii) the ability to demand usurious margins on Fixed Income and other products from clients trading in bulk who have no other middleman choices.