The other day I was musing about a reasonable approach to playing games like the big lotteries. They don't cost a lot and losing $40 is not a life changing event for me, but clearly winning a few hundred million dollars is life changing.
My first thought turned to, well if you just play when the expected value is greater than the cost of the ticket that is "rational". But when I started thinking about it, and even doing some calculations for when that EV condition exists (for things like Mega Millions the jackpot has to be greater then about 550 million) it struck me that the naive EV calculation must be missing something. The odds of actually winning the jackpot are really, really low (as opposed to just really low to rather low for the other prizes). And the payoffs that go into the EV calculation are hugely skewed by the top prices.
I suspect this must be a situation that generalized to other settings and am wondering if anyone knows of better approaches than merely the naive EV calculation. And to be sure I'm using the term as everyone expects, EV just equals the probability weighted payoffs minus the cost of the ticket.
Most people have non-linear utility of money. Going from 10 thousand to 1 million is less impactful than going from 1 million to 1.99 million, even though it's the same absolute change.
There's a tool called "certain equivalent" which can help with answering "how much do I value money?"
It boils down to repeatedly asking and answering question: "If I had a choice between $X and 50% of $Y at which X would I be ambivalent about which side I pick" for different value of $Y, e.g. for Bob, the 25 year old postdoc it may be
Notice how at higher level certain equivalent is no longer just dividing by two. For Bob utility from having $75k is higher than 50% of utility of having $400k. The reason for this nonlinearity is usually downstream effects of having money. E.g. for Bob $75k would be enough to get a downpayment for house he wants and highly increase chance of him a comfortable life down the line. 50% chance of buying the house outright is not worth the risk for Bob.