what do you mean when you say this is what Kelly instructs?
Kelly allocations only require taking actions that maximise the expectation of the joint distribution of log-wealth. It doesn’t matter how many bets are used to construct that joint distribution, nor when during the period they were entered.
If you don’t know at the start of the period which bets you will enter during the period, you have to make a forecast, as with anything unknown about the future. But this is not a problem within the Kelly optimisation, which assumes the joint distribution of outcomes already exists.
This is also how correlated risk is worked into a Kelly-based decision.
Simultaneous (correlated or independent) bets are only a problem in so far as we fail to construct a joint distribution of outcomes for those simultaneous bets. Which, yeah, sure, dimensionality makes itself known, but there’s no fundamental problem there that isn’t solved the same way as in the unidimensional case.
Edit: In more laymanny terms, Kelly requires that, for each potential combination of simultaneous bets you are going to enter during the period, you estimate the probability distribution of wealth outcomes (and this probability distribution should account for any correlations) after the period has passed. Given that, Kelly tells you to choose the set of bets (and sizes in each) that maximise the expected log of wealth outcomes.
Kelly is a function of actions and their associated probability distributions of outcomes. The actions can be complex compound actions such as entering simultaneous bets—Kelly does not care, as long as it gets its outcome probability distribution for each action.
Ah, my “what do you mean” may have been unclear. I think you took it as, like, “what is the thing that Kelly instructs?” But what I meant is “why do you mean when you say that Kelly instructs this?” Like, what is this “Kelly” and why do we care what it says?
That said, I do agree this is a broadly reasonable thing to be doing. I just wouldn’t use the word “Kelly”, I’d talk about “maximizing expected log money”.
But it’s not what you’re doing in the post. In the post, you say “this is how to mathematically determine if you should buy insurance”. But the formula you give assumes bets come one at a time, even though that doesn’t describe insurance.
I just wouldn’t use the word “Kelly”, I’d talk about “maximizing expected log money”.
Ah, sure. Dear child has many names. Another common name for it is “the E log X strategy” but that tends to not be as recogniseable to people.
you say “this is how to mathematically determine if you should buy insurance”.
Ah, I see your point. That is true. I’d argue this isolated E log X approach is still better than vibes, but I’ll think about ways to rephrase to not make such a strong claim.
Kelly allocations only require taking actions that maximise the expectation of the joint distribution of log-wealth. It doesn’t matter how many bets are used to construct that joint distribution, nor when during the period they were entered.
If you don’t know at the start of the period which bets you will enter during the period, you have to make a forecast, as with anything unknown about the future. But this is not a problem within the Kelly optimisation, which assumes the joint distribution of outcomes already exists.
This is also how correlated risk is worked into a Kelly-based decision.
Simultaneous (correlated or independent) bets are only a problem in so far as we fail to construct a joint distribution of outcomes for those simultaneous bets. Which, yeah, sure, dimensionality makes itself known, but there’s no fundamental problem there that isn’t solved the same way as in the unidimensional case.
Edit: In more laymanny terms, Kelly requires that, for each potential combination of simultaneous bets you are going to enter during the period, you estimate the probability distribution of wealth outcomes (and this probability distribution should account for any correlations) after the period has passed. Given that, Kelly tells you to choose the set of bets (and sizes in each) that maximise the expected log of wealth outcomes.
Kelly is a function of actions and their associated probability distributions of outcomes. The actions can be complex compound actions such as entering simultaneous bets—Kelly does not care, as long as it gets its outcome probability distribution for each action.
Ah, my “what do you mean” may have been unclear. I think you took it as, like, “what is the thing that Kelly instructs?” But what I meant is “why do you mean when you say that Kelly instructs this?” Like, what is this “Kelly” and why do we care what it says?
That said, I do agree this is a broadly reasonable thing to be doing. I just wouldn’t use the word “Kelly”, I’d talk about “maximizing expected log money”.
But it’s not what you’re doing in the post. In the post, you say “this is how to mathematically determine if you should buy insurance”. But the formula you give assumes bets come one at a time, even though that doesn’t describe insurance.
Ah, sure. Dear child has many names. Another common name for it is “the E log X strategy” but that tends to not be as recogniseable to people.
Ah, I see your point. That is true. I’d argue this isolated E log X approach is still better than vibes, but I’ll think about ways to rephrase to not make such a strong claim.