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# Monthly Archives: May 2013

## Value at Risk with exponential smoothing

More accurate than historical, simpler than garch. Previously We’ve discussed exponential smoothing in “Exponential decay models”. The same portfolios were submitted to the same sort of analysis in “A look at historical Value at Risk”. Issue Markets experience volatility clustering. As the previous post makes clear, historical VaR suffers dramatically from this. An alternative is … Continue reading

## US market portrait 2013 week 21

US large cap market returns. Previous posts had the charts off by a day, and no one had the grace to say. The halving of DF is technically correct, but financially misleading. There was a spin-off where the other half of the value went. Fine print The data are from Yahoo Almost all of the … Continue reading

## Implied alpha and minimum variance

Under the covers of strange bedfellows. Previously The idea of implied alpha was introduced in “Implied alpha — almost wordless”. In a comment to that post Jeff noticed that the optimal portfolio given for the example is ever so close to the minimum variance portfolio. That is because there is a problem with the example … Continue reading

Posted in Quant finance, R language
Tagged implied alpha, minimum variance portfolio, reverse optimization
7 Comments

## US market portrait 2013 week 20

US large cap market returns. Fine print The data are from Yahoo Almost all of the S&P 500 stocks are used (as implied by Wikipedia on 2013 January 5 — see the R commands to scrape the data) The initial post was “Replacing market indices” The R code is in marketportrait_funs.R — you are free … Continue reading

## Variance matrix differences

Torturing portfolios to give different volatilities between a factor model and Ledoit-Wolf shrinkage. Previously There have been posts on: “What the hell is a variance matrix?” factor models Ledoit-Wolf shrinkage Question Two of the several ways to produce an estimate of the variance matrix of asset returns is a statistical factor model and Ledoit-Wolf shrinkage. … Continue reading

## US market portrait 2013 week 19

## The half variance approximation for mean returns

What’s that thing about arithmetic and geometric returns and the variance? Previously An introduction to the difference between simple and log returns is: A tale of two returns Issue Suppose you are predicting the mean annual return of an asset for some number of years. To simplify the discussion, let’s buy into the fantasy that … Continue reading