Hi Jim,

Thanks for the info, that helped quite a bit. For some reason when I start with Jan 2008 I can't quite get 0 for the mean of the spread from the line, I get -1.5% (which is weird, since I am dividing by the mean of both the WMA and the adjusted close).

Using the data since 2008, I have the following results:

For 7/22/2025, I have BRK-B close at 478.13, and a CPI adjusted close at 149.84. The CPI Adjusted WMA is 1278, and the ratio to match is 9.77, thus the matching WMA is 130.86

The standard deviation of pricing is 11.47%

If I then reverse the CPI calculation, the trendline is 417.6, and the CALL is at 465 and the PUT at 370.

This seems to match what you had, but the last thing I need to keep track of this in realtime is the source of CPI data you are using.

Thanks, G.

PS: When I do a histogram of the deviation from trendline from 2008 to now, it isn't a great gaussian fit, it has a peak at -15-18%, and much peakier around 0 than a gaussian would be. Doing a plot of the CPI adjusted WMA and closing prices (logy) very much shows the price going up and down around the trendline.