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.
Even with compute power available, the "value" part of EV calculations gets weird outside of the bounds of normal experience. Very small probabilities are susceptible to estimation error, and very large impacts are susceptible to value error.
For the lottery specifically, for most non-impoverished people, the ranges of reasonable estimates are such that it's rationally justifiable to play or not play, depending on your enjoyment of the act rather than the monetary EV. The actual monetary EV is only a guess anyway - given that more tickets get sold when it's large, the chance of splitting the win goes up, and that's ignoring the chance of errors, cheating, or other shenanigans. Add to that the fact that you don't know how it changes your life and relationships to win - it's probably quite positive, but it's impossible to predict how much.
It was popular in the 90s among positive-ev gambling folks (card counters and the like) to search the world for +EV lotteries and pool funds to buy LOTS of non-overlapping tickets. True opportunities were somewhat scarce, and usually the smaller ones, not the giant jackpots.
I made some profit in card counting and poker, and made friends with some of the pros - there were definitely profitable teams and syndicates, and part of their profits was in identifying broken games and exploiting them until fixed. I had a decent job at the time, and didn't really want to commit that much energy to it, so I remained a hobbyist and hanger-on.
I knew about a number of progressive slot jackpots that were +EV for periods of time, a bunch of promo or just miscalculated bonus bets at small casinos, suspiciously-generous Keno payouts, and... (read more)