Thanks for your comment, David. I should point out--though you probably already know it--that an actual volatility number (say, 12.3%) doesn't mean a whole lot unless you know the frequency of the data that was used to compute it, and also whether it has been or needs to be corrected for autocorrelation. Extraordinarily low volatilities are often quoted for illiquid assets, such as non-traded real estate, but those are meaningless because they aren't corrected for measurement problems. But if you're comparing volatility over time for the same type of asset with the same methods for measuring it, then you can certainly say something worthwhile about how volatility has changed.