For a complete list of Beginners articles, see the Financial Crisis for Beginners page.
Joe Nocera has an article in today’s New York Times Magazine about Value at Risk (VaR), a risk management technique used by financial institutions to measure the risk of individual trading desks or aggregate portfolios. Like many Magazine articles, it is long on personalities (in this case Nassim Nicholas Taleb, one of the foremost critics of VaR) and history, and somewhat light on substance, so I thought it would be worth a lay explanation in my hopefully by-now-familiar Beginners style.
VaR is a way of measuring the likelihood that a portfolio will suffer a large loss in some period of time, or the maximum amount that you are likely to lose with some probability (say, 99%). It does this by: (1) looking at historical data about asset price changes and correlations; (2) using that data to estimate the probability distributions of those asset prices and correlations; and (3) using those estimated distributions to calculate the maximum amount you will lose 99% of the time. At a high level, Nocera’s conclusion is that VaR is a useful tool even though it doesn’t tell you what happens the other 1% of the time.
naked capitalism already has one withering critique of the article out. There, Yves Smith focuses on the assumption, mentioned but not explored by Nocera, that the events in question (changes in asset prices) are normally distributed. To summarize, for decades people have known that financial events are not normally distributed – they are characterized by both skew and kurtosis (see her post for charts). Kurtosis, or “fat tails,” means that extreme events are more likely than would be predicted by a normal distribution. Yet, Smith continues, VaR modelers continue to assume normal distributions (presumably because they have certain mathematical properties that make them easier to work with), which leads to results that are simply incorrect. It’s a good article, and you’ll probably learn something.
While Smith focuses on the problem of using the wrong mathematical tools, and Nocera mentions the problem of not using enough historical data – “All the triple-A-rated mortgage-backed securities churned out by Wall Street firms and that turned out to be little more than junk? VaR didn’t see the risk because it generally relied on a two-year data history” – I want to focus on another weakness of VaR: the fact that the real world changes.
Continue reading “Risk Management for Beginners”
One of our readers recommended the Congressional testimony by Andrew Lo during last Thursday’s session on hedge funds. Lo is not only a professor at the MIT Sloan School of Management, but the Chief Scientific Officer of an asset management firm that manages, among other things, several hedge funds. He discusses a topic – systemic risk – that has been thrown around loosely by many people, including me, and tries to define it and suggest ways of measuring it. He recommends, among other things, that
- large hedge funds should provided data to regulators so that they can measure systemic risk
- the largest hedge funds (and other institutions engaged in similar activities) should be directly overseen by the Federal Reserve
- financial regulation should function on functions, such as providing liquidity, rather than institutions, which tend to change in ways that make regulatory structures obsolete
- a Capital Markets Safety Board should be established to investigate failures in the financial system and devise appropriate responses
- minimum requirements for disclosure, “truth-in-labeling,” and financial expertise be established for sales of financial instruments (such as exist, for example, for pharmaceuticals)
Lo also has a talent for explaining seemingly arcane topics in language that should be accessible to the readers of this site. The testimony is over 30 pages long, but it’s a good read. Here are a couple of examples to whet your appetite.
Continue reading “Systemic Risk, Hedge Funds, and Financial Regulation”
Since the Lehman credit default swaps settled without the sky falling, there has been a small wavelet of support for the once-obscure financial instruments that are widely blamed for amplifying the effects of the financial crisis, including a Forbes.com op-ed entitled “Credit Default Swaps Are Good for You.” I happen to agree that CDS can play a useful role in enabling bond investors to hedge against the risk of default, and thereby make it easier for some institutions to get credit. But it’s a bit premature to proclaim that all is well and good in swapland.
Most obviously, there is the troubling matter of AIG, which has recently received additional scrutiny from the likes of the New York Times and the Wall Street Journal (subscription required). AIG has already burned through most of its initial $85 billion loan from the government, has drawn down half of a separate $38 billion loan for its securities lending business, and recently got permission to sell up to $20 billion of commercial paper to the Fed. (And remember, when negotiations over the AIG bailout began around September 12, the company was saying it only needed $20 billion.)
Continue reading “AIG, Credit Default Swaps, and “Risk Management””