gjm comments on Iterated Gambles and Expected Utility Theory - Less Wrong

1 Post author: Sable 25 May 2016 09:29PM

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Comment author: gjm 06 June 2016 03:07:36PM -1 points [-]

log utility is not sufficient to explain risk aversion.

In fact it's pretty well established that typical levels of risk aversion cannot be explained by any halfway-credible utility function. A paper by Matthew Rabin shows, e.g., that if you decline a bet where you lose $100 or gain $110 with equal probability (which many people would) and this is merely because of the concavity of your utility function, then subject to rather modest assumptions you must also decline a bet where you lose $1000 or gain all the money in the world with equal probability.

Comment author: Lumifer 06 June 2016 04:14:25PM *  2 points [-]

In fact it's pretty well established that typical levels of risk aversion cannot be explained by any halfway-credible utility function.

Yep, I've been mentioning that on LW over and over again, but people seem reluctant to accept that.

Comment author: gjm 06 June 2016 03:23:53PM -1 points [-]

There was some discussion of that paper and its ideas on LW in 2012. Vaniver suggests that the results may be more a matter of eliciting people's preferences in a lazy way that doesn't get at their real, hopefully better thought out, preferences. (But I fear people's actual behaviour matches that lazy preference-elicitation pretty well.) There are some other interesting comments there, too.

Comment author: Good_Burning_Plastic 07 June 2016 07:01:13AM 0 points [-]

any halfway-credible utility function

Some of those conclusions are not as absurd as Rabin appears to believe; I think he's typical-minding. Most people will pick a 100% chance of $500 over a 15% chance of $1M.

with equal probability

Prior or posterior to the evidence provided by the other person's willingness to offer the bet? ;-)

rather modest assumptions

Such as assuming that that person would also decline the bet even if they had 10 times as much money to start with? That doesn't sound like a particularly modest assumption.