I think IUCN number, which is counting extinctions since 1500 AD, is good. They have an explicit list of species they’re classifying as extinct (927 of them as of this writing: stats), and they’re cognizant of the problem of overcategorizing them:
the intention is generally to be extremely precautionary about categorizing taxa as EX or EW. An erroneous extinction classification can have several unfortunate consequences. It can bring the list into disrepute, but more seriously, it can lead to the “Romeo error,” whereby a species is believed to be extinct so conservation funding, habitat protection, and even surveys cease before it is really too late
(doi:10.1111/j.1523-1739.2008.01044.x)
They also have a list of 1381 species they think are probably extinct, but still list as “critically endangered” because they don’t think they’ve looked hard enough yet.
I think IUCN number, which is counting extinctions since 1500 AD, is good. They have an explicit list of species they’re classifying as extinct (927 of them as of this writing: stats), and they’re cognizant of the problem of overcategorizing them:
(doi:10.1111/j.1523-1739.2008.01044.x)
They also have a list of 1381 species they think are probably extinct, but still list as “critically endangered” because they don’t think they’ve looked hard enough yet.