to me “no belief” often means that people have a lot of uncertainty about their probability estimates. I think that this uncertainty can be best expressed by asking people to make a market on their probability estimate, rather than just specifying a single number. So, for instance if you asked me to make a market in the probability that a fair coin toss will come up heads, I will be like 49@51, (I’ll buy 49% and I’ll sell 51% because I am very confident that the true value is 50% and so I know I am getting some edge on that one). If you ask me the probability that someone currently being stored at alcor will be brought back to life at some point in the future, I have very little confidence about how to estimate that, and so I’ll be something like .0001 bid @ 85 offer.
If you take your beliefs seriously you should be willing to bet on them. If you are willing to bet on them they should be 2-sided markets and not single numbers because you should not be willing to take either side of a bet with the same odds, even a coin flip, because you have 0 EV at best. Once you consider credit risk, transaction costs, adverse selection, etc. then you are definitely -EV unless you include a bid/ask spread.
to me “no belief” often means that people have a lot of uncertainty about their probability estimates. I think that this uncertainty can be best expressed by asking people to make a market on their probability estimate, rather than just specifying a single number. So, for instance if you asked me to make a market in the probability that a fair coin toss will come up heads, I will be like 49@51, (I’ll buy 49% and I’ll sell 51% because I am very confident that the true value is 50% and so I know I am getting some edge on that one). If you ask me the probability that someone currently being stored at alcor will be brought back to life at some point in the future, I have very little confidence about how to estimate that, and so I’ll be something like .0001 bid @ 85 offer.
If you take your beliefs seriously you should be willing to bet on them. If you are willing to bet on them they should be 2-sided markets and not single numbers because you should not be willing to take either side of a bet with the same odds, even a coin flip, because you have 0 EV at best. Once you consider credit risk, transaction costs, adverse selection, etc. then you are definitely -EV unless you include a bid/ask spread.
This seems like a similar point to When (Not) To Use Probabilities—would you agree?