A third, more specific point is that the VAR approach is useless because volatilities and correlations change over time. This is debatable. Even when changes occur, the degree of precision in daily volatilities is much higher than that in expected returns. Traders routinely take positions based on views that are even less reliable than risk measures. It is difficult to tell whether traders are right or wrong; we do know, however, when they are taking large risks. Also, we have successfully learned to model volatilities that change over time (such as using GARCH models). Even better, we can use risk measures implied from option data, which are the best forecasts one could expect. It seems to me that our goal should be to try to improve our risk forecasts, instead of discarding the whole VAR approach and relying on "market lore.