Enron Mail |
Ted,
An update on the implementation for FFVols: (1) In comparing 6 days of historical Var calculations (with that of the implied) for Agg-Gas, we have found that the Historical VaR calculations are consistently lower over this period, by roughly 17 MM. The implied volatilities are much higher at this period, anticipating strong winter prices. (2) At this time, the consensus is not to relase the historical implementation into production, and the official line to traders will be that the method is still in testing. The historical VaR is 19.2MM and the implied is 37 MM for effective date of 09/25. (3) Further testing is in progress on a hybrid methodology (which I mentioned last week, whereby historical vols are scaled by the ratio of prompt to historical-prompt volatilities), to atleast capture some implied/forward effects. Tanya's analysis on a fictitious portfolio indicates higher VaR numbers, but poorer backtesting in comparison to the historical approach. This approach serves as an intermediate, and seems appropriate in periods such as the current one, wherein the historical numbers might be considerably lower than those of the implied. (4) Winston will start testing using these hybrid vols, and if the results are deemed satisfactory, that will be the production methodology. Of course, we will obtain all VaR numbers concurrently to serve as different indicators and beacons of risk. The production number will hopefully be a sensible compromise of the different methods. Regards Naveen
|