July 17th, 2004, 1:41 pm
Hedge fund return distributions exhibit autocorrelation, negative skewness and kurtosis. Since you are simulating rather than solving equations, the simplest approach is to use two Normal distributions, one with positive mean and moderate standard deviation, and the other with large negative mean and large standard deviation. Each time step there is a transition probability, say 0.05 of going from the first to the second set of parameters and 0.5 of going from the second back to the first.I would capture the autocorrelation by simulating an independent series and taking a moving average, maybe an exponentially weighted one with a decay of 0.8 or so.Anyway, you can tweak the parameters, the two means and standard deviations, the two transition probabilities and the decay factor, to atch the empirical behavior of the funds you are studying. For most purposes you're not interested in the precise dynamics of the returns. If you're constructing a large portfolio of funds for long-term investment purposes, capturing the first few moments approximately correctly is sufficient.One big advantage of this approach is you can account for survivorship bias. You can simulate 1,000 funds for five years, and terminate all funds with drawdowns of more than 50% (for example). Then you adjust the parameters so the remaining funds match your actual data.