... Under the U.S. Federal Reserve Board's Regulation T and SEC Rule 15c3-3, a prime broker may re-hypothecate assets to the value of 140% of the client's liability to the prime broker. For example, assume a customer has deposited $500 in securities and has a debt deficit of $200, resulting in net equity of $300. The broker-dealer can re-hypothecate up to $280 (140 per cent. x $200) of these assets.
But in the UK, there is absolutely no statutory limit on the amount that can be re-hypothecated. In fact, brokers are free to re-hypothecate all and even more than the assets deposited by clients. Instead it is up to clients to negotiate a limit or prohibition on re-hypothecation. On the above example a UK broker could, and frequently would, re-hypothecate 100% of the pledged securities ($500).
This asymmetry of rules makes exploiting the more lax UK regime incredibly attractive to international brokerage firms such as MF Global or Lehman Brothers which can use European subsidiaries to create pools of funding for their U.S. operations, without the bother of complying with U.S. restrictions.
In fact, by 2007, re-hypothecation had grown so large that it accounted for half of the activity of the shadow banking system. Prior to Lehman Brothers collapse, the International Monetary Fund (IMF) calculated that U.S. banks were receiving $4 trillion worth of funding by re-hypothecation, much of which was sourced from the UK. With assets being re-hypothecated many times over (known as “churn”), the original collateral being used may have been as little as $1 trillion – a quarter of the financial footprint created through re-hypothecation.
BEWARE THE BRITS: CIRCUMVENTING U.S. RULES
Keen to get in on the action, U.S. prime brokers have been making judicious use of European subsidiaries. Because re-hypothecation is so profitable for prime brokers, many prime brokerage agreements provide for a U.S. client’s assets to be transferred to the prime broker’s UK subsidiary to circumvent U.S. rehypothecation rules...
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http://newsandinsight.thomsonreuters.com/Securities/Insight/2011/12_-_December/MF_Global_and_the_great_Wall_St_re-hypothecation_scandal/And from the first link (essential reading):
... it was not only the repo market, but the far broader and massively unregulated shadow banking system in Europe that was becoming thoroughly unhinged, and was manifesting itself in a complete "lock up in interbank liquidity" and which, we speculated, is pressuring the Bundesbank, which is well aware of what is going on behind the scenes, to slowly back away from what will soon be an "apocalyptic" event (not our words... read on). ...
... a symptom of two things: i) the lax London-based unregulated and unsupervised system which has allowed such unprecedented, leveraged monsters as AIG, Lehman and now as it turns out MF Global, to flourish until they end up imploding and threatening the world's entire financial system, and ii) an implicit construct embedded within the shadow banking model which permitted the heaping of leverage upon leverage upon leverage, probably more so than any structured finance product in the past (up to and including synthetic CDO cubeds), and certainly on par with the AIG cataclysm which saw $2.7 trillion of CDS notional sold with virtually zero margin. Simply said: when one truly digs in, MF Global exposes the 2011 equivalent of the 2008 AIG: virtually unlimited leverage via the shadow banking system, in which there are practically no hard assets backing the infinite layers of debt created above, and which when finally unwound, will create a cataclysmic collapse of all financial institutions, where every bank is daisy-chained to each other courtesy of multiple layers of "hypothecation, and re-hypothecation." ...
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http://www.zerohedge.com/news/why-uk-trail-mf-global-collapse-may-have-apocalyptic-consequences-eurozone-canadian-banks-jeffe