Tuesday, 16 June 2009

The Amherst Trade

This is a geeky post about the CDS market.

The newswires have been buzzing recently with news of a 'daring' CDS trade by Amherst Holdings. I didn't comment on it at first as I didn't understand the trade from the initial news items, but I now think it is possible to work out what's going on.

Let's start with the bonds this trade refers to. They are subprime MBS. Like most MBS, these are amortising, prepayable bonds. The fact that these are amortising bonds means that the face value of the security is irrelevant: what counts is the principal balance at the time the trade was done. [Quite a lot of the stories were confused about this point, so it is worth pointing out.]

So, let's say we have some bonds with $100M left to repay.

The next bit that is tricky is the nature of the CDS protection sold. Everyone agrees Amherst sold protection and some banks bought it. But what protection exactly? It is most common for CDS on MBS to be pay as you go, meaning that the protection sellers compensates the protection buyer for principal deficiencies as and when they occur. There is no event of default as such, unlike corporate CDS. [To be strictly honest, there may be an event of default as well, such as bankruptcy of the issuing SPV, but that is irrelevant for our purposes.]

Let's suppose then that Amherst sold pay as you go protection on $100M of bonds.

Since the bonds were thought likely to repay little to nothing of the outstanding principal balance, the banks paid Amherst, say, $80M up front for their protection. [There may have been an ongoing coupon as well, but we'll ignore that.]

Amherst then paid the servicer to buy out the underlying mortgages and pay off the bonds. Thus the bond holders got their $100M. The servicer could do this because the bonds had a 10% clean up call, meaning that if more than 90% of the face had amortised, they could repay the remaining principal balance at any time. [So to keep with the example, the face amount was more than $1B.] 10% cleanup calls are common in ABS, and they are what makes Amherst's trade work*.

Now, here's the confusing part. Who won and who lost?

First the banks. If they had held the bonds, then they would be about flat. $80M for CDS protection paid out, but $100M paid back is a $20M profit, from which subtract the (few cents) cost of the bonds. So the only way the banks could have lost massively on the trade, as reported, would have been if they had been net short the bonds. That is, they did not own the bonds, and bought protection, betting that total losses would be more than $80M. The losers, then, were parties who did not own the bonds and who did not realise the significance of the cleanup call to their short.

[The WSJ story suggests that JP Morgan lost money but that RBS and BofA didn't. This would be consistent with JP being net short, while RBS and BofA had a negative basis trade on, i.e. owned the bonds and bought CDS on them. The presence of net shorts is also consistent with the WSJ's suggestion that more protection had been traded than the notional of bonds outstanding.]

Next Amherst. They had the $80M of CDS premium. But how much did they have to pay to get the bonds repaid? Clearly a logical answer would be about $80M. Therefore the only way that Amherst could have made money would have been if they had sold more protection than there were bonds - $200M say rather than $100M. Say they sold $50M to JPM, $50M to RBS and $50M to BofA. Then they would have had to pay $80M, roughly, to buy back the mortgages behind the RBS and BofA CDS, but the JPM CDS was not backed by any bonds and so the $40M premium from JPM would be straight profit.

In other words, the only way Amherst could have made a lot of money on this trade would have been if it sold more protection than there were bonds. The only way that the banks could have lost money would have been if they bought more protection than there were bonds. In a situation like this someone was always going to be squeezed. It's just that this time, that party wasn't an investment bank.

The lesson of this amusing little situation? Nothing more than read the small print. The buyers of protection -- and in particular naked shorts -- should have understood that arbitrary action by servicers is possible, and that in particular the 10% clean up call could be exercised. This is a much bigger risk late in the amortisation profile of a bond than early, but it is there for most ABS. Caveat emptor.

* Contrary to what Willem Buiter writes in his blog, if you own 100% of a bond, you cannot necessarily control whether it defaults or not. A default on a public security is a default, regardless of who is affected.

Another mistake Buiter makes is assuming that centralising CDS trading would not have helped in this situation. It would certainly have helped the banks to avoid their losses, in that the size of Amherst's long vs. the cash would have been obvious thanks to trade reporting. Personally I don't particularly feel the need to help the CDS trading desks of investment banks, mind you.

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Blogger Dave said...

Thanks for the explanation. It is much more thorough and convincing than others that I have seen.

The spin on this story is typically how crazy the CDS market is. But surely, an equivalent trade could happen in any derivative whose holder has a bigger position than the total value of the underlying security: eg holding put options on 100,000 shares on a company whose total capitalisation is 50,000 shares.

So, all that is crazy here is that the banks held such big positions on such a small MBS issue. Why do you think that they did this? Was it pure speculation, or were they trying to hedge other, related MBS's which don't have CDSs traded?

12:47 am  
Blogger David Murphy said...

It was a basis hedge. There are so many MBS out there that buying protection on the one you own is difficult. Buying protection on one that is similar is usually viewed as good enough. Because there is little effective trade reporting in the CDS market, it is difficult to know who has done what, and hence difficult to know that more protection has been sold than the bonds outstanding.

11:03 pm  
Blogger Dave said...

OK, thanks for the response. That certainly hasn't come out in the other reports I've seen. They seem to think the CDS buyers were gambling, not hedging. But, I suppose that makes a better story.

11:31 pm  

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