Final Update: Given the low levels late in the year for 2018 I decided just to wait until May 1st before a final update. The maximum drawdown level for 2018 came on March 27th at 653.91. A very typical peak low level. Nine year data average for date and level is now March 11th, at an average level of 654.82.
Below is a simple graph of just 9 year hourly levels average. (= Green graph above)