[alThor]

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If your risk of ruin exceeds 13%, then if you can move down in stakes, you certainly should.

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I think this is too strong of a statement.

I know where it's coming from: (1) If you are currently playing at full Kelly, and will never resize bets (i.e. change stakes), then your ROR is around 13% (or 13.5%, whatever). (2) If you are resizing your stakes/bets as your bankroll changes, then you don't want to bet more than full Kelly (to max your growth).

I think you are using (2) and (1) together to make your statement that "ROR above 13% is always bad". But note that the two statements apply to different scenarios: whether or not you resize.

A person who wants high EV and is less concerned about ruin may very well have a ROR above 13%. I don't think it's common, nor would I advise anyone to do this in most situations. Nevertheless, I don't think we should proclaim 13% ROR as the highest permissible one, absolutely.

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Probably you want to keep your ROR under 1%.

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This is very conservative for people who can replenish their bankrolls. It would often be better to set a higher ROR, but then resize (change stakes) if your bankroll drops significantly. In this case, your true ROR is lower than the the ROR you originally calculated, but your EV is going to be much higher.

If one is a retiree who plays to supplement his income, then a conservative ROR is certainly appropriate.

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These numbers all come from fractional Kelly betting theory.
For more on this topic see bjmath.com, especially the risk formula paper by BillC and Marc Ingenoso.

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Am I correct that you are a different BillC?