Bloomberg will shortly release the full results of its latest study of the subsidy in which it believes the biggest banks luxuriate. Good news for big banks: the putative annual subsidy is way down from the $83 billion total that, when released in March, sparked dozens of calls for big-bank break-up. Bad news for the behemoths: Bloomberg still thinks there’s a walloping annual subsidy which, even if down to “only” $14 billion last year, will still come out of big-bank hides if advocates win the “user charge” they soon will seek.

The way the federal budget is constructed, $14 billion (maybe just a rounding error on its own given the size of the federal account) turns fantabulous when scored over the ten-year budget cycle. Then, it’s a few aircraft carriers or a whole lot of social services – real money that will be particularly tempting if it comes not from ordinary taxpayers, but rather from the big banks increasingly seen as nothing more than bad boys by a large majority of the citizenry across the full political spectrum. To be sure, Republicans don’t like taxes, but many of them argue that user fees or similar assessments on big banks don’t violate their no-tax pledge because, they argue, the charge only reimburses taxpayers instead of imposing new federal taxes on them. In short, the Bloomberg number – down as it is from the old one – is potent.

But, is it right? This question is analytically critical even if politically irrelevant. It’s a hard one to answer because the data on which Bloomberg bases its conclusions are not yet fully available. But, even as outlined, the conclusions raise provocative questions.

Importantly, Bloomberg goes well beyond funding to contemplate the other benefits it thinks big-banks enjoy. So far, most industry self-defense has focused on this issue – rebutting suggestions that big banks have TBTF priced into their funding costs by mounting data derived after Dodd-Frank and factoring in lower spreads resulting not from implicit protections, but rather from the efficiency and capital-market access attendant to the biggest financial-services firms. Bloomberg focuses on funding, but – like the pending GAO subsidy study – goes well beyond it to look at presumed benefits the industry has yet to think through.

For example, Bloomberg looks – as GAO in fact is required to do – at FRB’s quantitative-easing exercise. Bloomberg cites here the difference between Federal Reserve MBS purchase rates and the interest rate on underlying mortgages in these pools of loans. But, is the spread here a subsidy? One could state, as Bloomberg does, that it is because big banks realize above-normal spreads on mortgages without the FRB’s QE purchases. Arguing that normal MBS spreads are fifty basis points, Bloomberg says that the 150 bps now enjoyed is a big-bank subsidy that should be priced into the charter.

But, as a study last year from the Federal Reserve Bank of New York posited, other factors also come into play. First, lots of lenders make mortgages, not just big banks, and most of them realize just the same large spreads. Second, the spreads may result from an ability to game the Fed, but they could just as easily – and, I think, far more plausibly – result from sharply higher legal, reputational and put-back risk. Fees charged by Fannie Mae and Freddie Mac also drive the sharp difference in nominal FRB interest rates and the cost of mortgage credit. The latter is a lot lower than it would be without QE3, but this still doesn’t mean that the FRB’s purchase price for MBS necessarily translates into a subsidy. If big banks got to keep it all, that might be the case, but even then one would have to prove that the spread resulted from TBTF benefits, not from greater market power or other endogenous factors separate and apart from investor expectations of immutable bail-out.

Bloomberg also looks at the rating-agency differential between the risk assessment made for big banks with and without TBTF expectations. Bloomberg cites a late-March Moody’s chart showing that JPMorgan would be junk without an implicit guarantee.

But, is the rating agency right? If history is any guide, not necessarily. No one argued that AAA tranches of subprime MBS enjoyed a “subsidy” when they were priced equivalent to U.S. Treasury obligations at the height of the MBS bubble. At the time, rating agencies said that’s just how they saw it from a credit-risk perspective. Now, it’s how they see it from a big-bank rescue vantage, even as every senior U.S. official argues that Dodd-Frank dooms TBTF.

The real vulnerability of big banks to TBTF comes not from the factors scored by Bloomberg. Rather, it derives from the remaining weakness in the Dodd-Frank orderly-liquidation authority (OLA). While the law is clear – no bail-out no how – the rules are vague in an incomplete.

Here, testimony delivered earlier this week from former Treasury Under Secretary and now Stanford professor John Taylor is worth a read. He agrees that OLA is unproven and incomplete. Importantly, Mr. Taylor goes on to say that the industry backstop for OLA – intended by Congress to prevent any suggestion of taxpayer support – is a back-door bail-out because nothing like it exists in ordinary corporate failure. If Congress can order your competitors to bail out your creditors – as OLA allows – then, Mr. Taylor argues, the financial market is just a stand-in for taxpayers and the bail-out is just as comfy even if it’s not directly costly to the U.S. Government. The testimony also challenges a recent industry OLA exercise in support of the single-point-of-entry protocol, raising some important issues in this vital arena.

Mr. Taylor also joins two Federal Reserve Bank presidents in criticizing the statutory discretion the FDIC has in OLA to protect some creditors over others. This, he rightly argues, is also different from bankruptcy because the strict priority order and judicial process is overridden in favor of governmental decision-makers who might be swayed at least as much by politics as policy.

Do these OLA flaws prop up a subsidy? Here, Mr. Taylor’s analysis falters. He cites Bloomberg’s old $83 billion number even though its flaws are manifold. So, even as one concedes that OLA needs a lot of work before big banks go bust like everyone else, the critical subsidy question is, I think, still unanswere.