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I've finally worked Peter's per-month gains into my backtesters (http://gritton.org/ws/). Now, instead of testing a screen for monthly, quarterly, semiannual or annual holds, you can hold stocks for any number of months from 1 all the way to 24.

2-month and 4-month holds may be worth looking at for shorter-term screens, or 18 and 24 month hold for annuals. You could try funny things like 5, 7, or 19 months if you've a mind to.

There are some rough edges in the tester, so expect some changes to creep in. I try to keep year-end gains so the per-year gains come out right, but I suspect they're at least a bit bogus if the holding period isn't divisible by 12 months. The RSS tester also isn't going to like holds that don't divide by 12, and the blender won't ever give you a balance unless you give it holds with a decent common denominator.

There are also some holes in the gains data. It the process of searching these out and ettempting to fill them, I've gained further appreciation for Peter's work. Did you know that there were some stocks in the 70's that were publicly traded but don't have ticker symbols? And back then, Value Line didn't even include ticker symbols for those stocks that had them - Peter had to match up everything by company name. And then there are the Canadian stocks which he paid to get historical quotes for. Remember his charity portfolio. Where was I? Ah yes - there are holes in the gains, but not many. For that matter, there have always been some holes in the 1/3/6/12 month holds and we seem to have survived. As part of this project, I've also finally gotten around to 2000 gains, but I'm not quite done, so expect holes there too for a bit.

Now I need to make yet more changes to the testers. The Blend and Dozens testers can finally get around the hurdle of not knowing the mid-hold gains for longer-hold screens. I can add the GSD(M), once I figure out the formula, to give a more accurate picture of volatility (from more data points). Future work includes buying integral numbers of shares and working with dividends, but I don't have the data for that yet.

- Jamie
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