Category Archives: Risk

Effective risk management with R

Conference The first EARL Conference (Effective Applications of the R Language) was held 2014 September 15-17 in London. Talk My talk was “Effective risk management with R” (annotated slides). Instability hypothesis When I was preparing for the talk, one of my ideas was to show the Google trend for searches for Minsky’s instability hypothesis.  I … Continue reading

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Historical Value at Risk versus historical Expected Shortfall

Comparing the behavior of the two on the S&P 500. Previously There have been a few posts about Value at Risk (VaR) and Expected Shortfall (ES) including an introduction to Value at Risk and Expected Shortfall. Data and model The underlying data are daily returns for the S&P 500 from 1950 to the present. The VaR and … Continue reading

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Review of “Governance Reimagined” by David Koenig

The subtitle is “Organizational Design, Risk, and Value Creation”. Executive summary This should be a business book bestseller — it simply and clearly explains the process of value creation.  Its great disadvantage for bestsellerdom is that it doesn’t pretend there are magic bullets that create value. No one’s perfect. The gist I’ve met David a … Continue reading

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Changeability of Value at Risk estimators

How does Value at Risk change through time for the same portfolio? Previously There has been a number of posts on Value at Risk, including a basic introduction to Value at Risk and Expected Shortfall. The components garch model was also described. Issue The historical method for Value at Risk is by far the most commonly … Continue reading

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The scaling of Expected Shortfall

Getting Expected Shortfall given the standard deviation or Value at Risk. Previously There have been a few posts about Value at Risk and Expected Shortfall. Properties of the stable distribution were discussed. Scaling One way of thinking of Expected Shortfall is that it is just some number times the standard deviation, or some other number … Continue reading

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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

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An infelicity with Value at Risk

More risk does not necessarily mean bigger Value at Risk. Previously “The incoherence of risk coherence” suggested that the failure of Value at Risk (VaR) to be coherent is of little practical importance. Here we look at an attribute that is not a part of the definition of coherence yet is a desirable quality. Thought … Continue reading

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The incoherence of risk coherence

What coherent risk measures are, why some people think coherence is important, and why I don’t. The rules A risk measure is considered to be coherent if it satisfies some mathematical properties.  They are formulated in various ways — here is one set: (monotonicity) If the value of portfolio X is always bigger than the … Continue reading

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A look at historical Value at Risk

Historical Value at Risk (VaR) is very popular because it is easy and intuitive: use the empirical distribution of some specific number of past returns for the portfolio. Previously “The estimation of Value at Risk and Expected Shortfall” included an R function to estimate historical VaR. Generating portfolios A useful tool to explore risk models … Continue reading

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The estimation of Value at Risk and Expected Shortfall

An introduction to estimating Value at Risk and Expected Shortfall, and some hints for doing it with R. Previously “The basics of Value at Risk and Expected Shortfall” provides an introduction to the subject. Starting ingredients Value at Risk (VaR) and Expected Shortfall (ES) are always about a portfolio. There are two basic ingredients that … Continue reading

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