It seems that SIA says that the parameters of the drake equation should be expected to be optimized for observers-which-could-be-us to appear, but exactly this consideration was not factored into the calculations of Sandberg, Drexler, and Ord. Which would mean their estimations for the expected number of civilizations per galaxy are way too low.
SIA is a reason to expect very low values of N to be unlikely, since we would be unlikely to exist if N was that low. But the lowest values of N aren’t that likely—probability of N<1 is around 33%, but probability of N<10^-5 is around 15. It seems there’s at least a 10% chance that N is fairly close to 1, such that we wouldn’t expect much of a filter. This should carry through to our posterior such that there’s a 10% chance that there’s no future filter.
I don’t think this is correct. Look at page 6 of https://arxiv.org/pdf/1806.02404.pdf
SIA is a reason to expect very low values of N to be unlikely, since we would be unlikely to exist if N was that low. But the lowest values of N aren’t that likely—probability of N<1 is around 33%, but probability of N<10^-5 is around 15. It seems there’s at least a 10% chance that N is fairly close to 1, such that we wouldn’t expect much of a filter. This should carry through to our posterior such that there’s a 10% chance that there’s no future filter.