Here’s a good Sonic Charmer post about how JPMorgan could have prevented the London Whale loss by imposing a liquidity provision on the Whale’s desk:
Liquidity provision means: ‘the more illiquid the stuff you’re trading, the more rainy-day buffer we’re going to withhold from your P&L’. And since one way a thing becomes illiquid is ‘you’re dominating the market already’, you inevitably make it nonlinear, like a progressive income tax: No (extra) liquidity provision on the first (say) 100mm you own, half a point on the next (say) 400mm, a point on the next 500mm, 2 points on the next 1000mm, etc etc. (specific #s depend on the product). Problem solved. In fact, it’s genuinely weird and dumb if they didn’t have such a thing.
The London Whale’s problem (one of them) was that he traded so much of a particular thing that he basically became the market in it. That means among other things that even if on paper “The Price” of what he owned was X there would have been no way for him to sell the position for X. A liquidity provision is a rough and dirty way of acknowledging this fact.
This suggestion isn’t a matter of GAAP accounting: JPMorgan wouldn’t report its asset values, or its revenues, net of this liquidity provision. It’s just an internal bookkeeping mechanism: his bosses informing the Whale that, for purposes of calculating his P&L and, thus, his comp, they would take the GAAP value of the things he had and subtract a semi-arbitrary number for their own protection.
It is weird and dumb that they didn’t do this although you can sort of guess why: the Whale portfolio started very small, and by the time it got big the Whale was both profitable and a (mostly imaginary) tail risk hedge, so it would have been hard for a risk manager to take a semi-punitive step to rein in his risk-taking. “Just tell the Whale to take less risk” does in hindsight seem like a sensible suggestion, but I suppose if he’d made $6 billion it wouldn’t.