lec15 - Feb05_10

lec15 - Feb05_10 - CS476/676 Feb 5, 2010 Black Swans, VaR,...

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Unformatted text preview: CS476/676 Feb 5, 2010 Black Swans, VaR, and Risk Managment Yuying Li University of Waterloo 1 CS476/676 Feb 5, 2010 Who Is To Blame? Greedy executives, home buyers (who couldn’t afford), Feds, Fannie Mae, complex derivatives (MBS,CDOs, CDS), Quants, economists, ¡ ¡ ¡ Then it became more personal ¡ ¡ ¡ 2 Was David Li the guy who 'blew up Wall Street?' http://www.cbc.ca/canada/story/2009/04/08/f-mathwhiz.html Profile Financial Meltdown Was David Li the guy who 'blew up Wall Street?' Last Updated: Thursday, April 9, 2009 | 10:16 AM ET by Mike Hornbrook CBC News Described as both "modest" and "outgoing" by his former professors at the University of Waterloo, David Li is a Canadian math whiz who, some now say, developed the risk formula that destroyed Wall Street. When the full history of the Great Meltdown is written — presumably sometime after all the financial pain has eased — Li may occupy a special place. David Li in an undated photo. The formula he devised was widely used and helped some of America's biggest financial institutions determine how to market the controversial instruments known as credit derivatives, including what risk they faced, what strategies they needed to minimize the risk and what return they should demand. These days Li, 45, is in China, the country where he was born, keeping a low profile. He heads the risk-management department of China International Capital Corporation in Beijing. The company won't make him available for interviews. But according to friends, Li is said to be "sheepish" about all the trouble he has caused. Rise of the quants David Xiang Li obtained his Canadian citizenship in the 1990s and after completing his education here went to work on Wall Street as a quant. Mike Hornbrook has been the economics correspondent for CBC Radio News since 2004, covering economic and financial trends as well as significant business stories. Before that, Mike spent a decade abroad as a foreign correspondent for CBC radio and television. Quants are "quantitative analysts" — math wizards who design computer models to assess risk, price the latest financial instruments and predict market movements. Quants grew to prominence on Wall Street in the bull markets of the late-1980s and '90s with the rise of ever more complex financial innovations. In 1997, Li landed a job on the New York trading floor of CIBC World Markets, which was then a pioneer in the emerging credit derivatives market. In those days, investment banks were seeking ways to pool corporate bonds and then re-sell these in chunks, as they were doing with mortgages. The bond pools were known as collateralized debt obligations or CDOs. CDOs were supposed to make investing less risky because the exposure was diffused. If you bet the farm on the bonds of a single company, for example, you could lose it all if that firm failed. Invest in the bonds of hundreds of companies, on the other hand — all packaged together and sliced into portions reflecting differing risk — and it was thought unlikely that you would suffer a big loss if a few go bust. At least that was the theory. 1 of 3 9/21/2009 9:17 AM RISK Mismanagement - What Led to the Financial Meltdown - NYTimes.com http://www.nytimes.com/2009/01/04/magazine/04risk-t.html?_r=1&ref=t... This copy is for your personal, noncommercial use only. You can order presentation-ready copies for distribution to your colleagues, clients or customers here or use the "Reprints" tool that appears next to any article. Visit www.nytreprints.com for samples and additional information. Order a reprint of this article now. January 4, 2009 Risk Mismanagement By JOE NOCERA ‘The story that I have to tell is marked all the way through by a persistent tension between those who assert that the best decisions are based on quantification and numbers, determined by the patterns of the past, and those who base their decisions on more subjective degrees of belief about the uncertain future. This is a controversy that has never been resolved.’ — FROM THE INTRODUCTION TO ‘‘AGAINST THE GODS: THE REMARKABLE STORY OF RISK,’’ BY PETER L. BERNSTEIN THERE AREN’T MANY widely told anecdotes about the current financial crisis, at least not yet, but there’s one that made the rounds in 2007, back when the big investment banks were first starting to write down billions of dollars in mortgage-backed derivatives and other so-called toxic securities. This was well before Bear Stearns collapsed, before Fannie Mae and Freddie Mac were taken over by the federal government, before Lehman fell and Merrill Lynch was sold and A.I.G. saved, before the $700 billion bailout bill was rushed into law. Before, that is, it became obvious that the risks taken by the largest banks and investment firms in the United States — and, indeed, in much of the Western world — were so excessive and foolhardy that they threatened to bring down the financial system itself. On the contrary: this was back when the major investment firms were still assuring investors that all was well, these little speed bumps notwithstanding — assurances based, in part, on their fantastically complex mathematical models for measuring the risk in their various portfolios. There are many such models, but by far the most widely used is called VaR — Value at Risk. Built around statistical ideas and probability theories that have been around for centuries, VaR was developed and popularized in the early 1990s by a handful of scientists and mathematicians — “quants,” they’re called in the business — who went to work for JPMorgan. VaR’s great appeal, and its great selling point to people who do not happen to be quants, is that it expresses risk as a single number, a dollar figure, no less. VaR isn’t one model but rather a group of related models that share a mathematical framework. In its most common form, it measures the boundaries of risk in a portfolio over short durations, assuming a “normal” market. For instance, if you have $50 million of weekly VaR, that means that over the course of the next week, there is a 99 percent chance that your portfolio won’t lose more than $50 million. That portfolio could consist of equities, bonds, derivatives or all of the above; one reason VaR became so popular is that it is the only commonly used risk measure that can be applied to just about any asset class. And it takes into account a head-spinning variety of variables, including diversification, leverage and volatility, that make up the kind of market risk that traders and firms face every day. Another reason VaR is so appealing is that it can measure both individual risks — the amount of risk 1 of 13 1/4/2009 6:14 PM Ë » Æ ´ ¸ ½¼µ ÓÖ ÉÙ ÒØ Ø Ø Ú Ê × Å Ò Ñ ÒØ ÒÒ Ð × ×Ø Ö× Ò ÖÙÔØ Ý Ù ØÓ °½º Ö Ò ×¸ Ø ÔØ ÐÅ Ò Ñ ÒØ ÐÐ ÓÒ ¿ ËÓÑ ÈÖ ÓÖ ¯½ ¯½ ÑÖ Ø Ö× ÇÖ Ò ÓÙÒØÝ ÐÓ×× ÓÒ ÒÚ ×ØÑ ÒØ× ¯ ÁÒ ½ ¯ ÁÒ ½ ¯ ¡¡¡ ¸ ÐÓ×× Ó ° ¼¼ Ñ ÐÐ ÓÒ ÓÖ ÓÐ ×Ø Ò Ò Íø ØÓ × ØÖ Ò ¸ ÓÛÒ ÐÐ Ó ÄÓÒ ¹Ì ÖÑ ´ÄÌ Åµº Ë » ´ ¸ ½¼µ Å Ö Ø Ö × Ø Ö × Ù ØÓ Ò Ò Ø Ú ÐÙ Ó ¬Ò Ò Ð ÔÓ× Ø ÓÒ Ù ØÓ Ò × Ò Ø Ú ÐÙ × Ó Ø ÙÒ ÖÐÝ Ò ÓÒ Û Ø ÔÓ× Ø ÓÒ Ô Ò × ÓÒ¸ º º¸ ×ØÓ ÔÖ ×¸ ÓÒ ×¸ Ü Ò Ö Ø ×¸ Ò ÓÑÑÓ ØÝ ÔÖ × Ø º Ö Ø Ö × Ø Ö × Ù ØÓ ÒÓØ Ö Ú Ò ÔÖÓÑ × Ö Ô ÝÑ ÒØ× ÓÒ ÓÙØ×Ø Ò Ò ÒÚ ×ØÑ ÒØ× ×Ù × ÓÒ ×¸ ÐÓ Ò׸ Ù× Ó ÙÐØ Ó Ø ÓÖÖÓÛ Öº ÇÔ Ö Ø ÓÒ Ð Ö × Ø Ö × Ù ØÓ Ò ÕÙ Ø ÓÖ ÔÖÓ ×׸ ×Ù × Ô ÓÔÐ ¸ ÓÑÔÙØ Ö ×Ý×Ø Ñ׸ Ø º Ð Ë » ´ ¸ ½¼µ ÀÓÛ Ó Û Ñ ×ÙÖ Ö × Ó ÖÚ ØÚ × Ê ØÙÖÒ ÓÖ ×Ù Ú Ò ×ÝÑÑ ØÖ ÔÓÖØ ÓÐ Ó Ò ÐÙ Ò ÔÓÖØ ÓÐ Ó × ØÝÔ ÖÓÙÒ Ñ Òº ÐÐÝ ÒÓØ ÒÓÖÑ Ð¸ ÓÖ Ë » ´ ¸ ½¼µ ÓÖ Ü ÑÔÐ ¸ ××ÙÑ Î × Ò ×ØÖ Ã º ××ÙÑ ÌÒ ÐÐ ÓÒ ×ØÓ ÛØ ÜÔ ÖÝ Ì ËØ ËØ Ø· ÏØ ÎØ µ ËØ Î Î Î ½ ¾ ¾ ¾Î · Ë ´ ¾ · Ë Ë µ Ø · Ë Ë ÏØ 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