Will MacAskill discussing asteroids with Joe Rogan, starting around 1:24:00 in this recording –
Rogan: When you think about how big that thing was, that killed the dinosaurs 65 million years ago, and that there are hundreds of thousands of those things floating around in space.
MacAskill: I was asking some people at NASA, just two days ago actually, how many of them we've managed to identify – cause they're serious about scanning the skies to find them all...
I thought we had it covered. I thought this was something where NASA was like "Yeah yeah, we know where all the earth-killers are."
And their response was like "No, we have no idea. We don't know how many of them are out there, and so we don't know [what proportion] we've managed to track."
Unlike other GCRs (e.g., nuclear war), asteroid risk is extremely quantifiable: scientists have estimated the number and size of near-earth asteroids and are able to track how many have been discovered.
I'm inclined to follow MacAskill here, as the Open Phil investigation is based on public sources and NASA may have incentive to overstate their handle on the problem in public-facing communications.
But I haven't looked into this closely. Has anyone in EA thought about asteroid risk, recently?
(It looks like this isn't totally neglected – the B612 Foundation was set up to "to protect Earth from asteroid impacts." I haven't poked them enough to know how good their stuff is.)