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5#
发表于 2013-8-11 19:26
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VaR can be useful for managing personal portfolios, but it is hard to explain what it means to clients who are not financial professionals, because saying “it means that you won’t lose more than 1.5%, 95% of the time” takes practice to understand (and because 5% of 250 trading days is still 12-13 days/year, or about once per month). It’s more useful as a way to try to convert your qualitative estimate of risk tolerance to some kind of quantitative threshold that you use for your own internal management, rather than a number you tell your client you are holding yourself to.
It shouldn’t be to difficult to do parametric var (where you assume something like a normal distribution of returns - or other distribution, but that does get more complex), because you just compute the standard deviation of the expected portfolio return and figure out where the 5% cutoff is (or whatever cutoff you are using). You need to know the mathematics, but the calculations aren’t all that difficult, particularly if you have some experience with matrix multiplication or a relatively small number of ETFs. You can also do historical VaR, which simply looks at the bottom X% of historically realized returns and figures out where the cutoff is. The challenge here is that some ETFs have very short histories, but you can often use the indexes that they track as a substitute. |
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