[joemag]

It comes with a bias though, since your searches will bias towards finding asteroids that are easiest to find using your search method.

[ccapo]

Correct, and since that bias is towards larger NEOs, which are relatively easier to detect then smaller objects, they can be reasonably confident about that estimate. It is the medium to small size NEOs that are the most worrisome. They are harder to detect, and hence harder to estimate how many are out there.

[BurningFrog]

Seems like a bigger problem for turtles than for asteroids.

I mean, asteroids don't deliberately hide.

Sure, some are darker and/or have a less visible radar profile or whatever, but the variations seem manageable.

[craftyguy]

They don't deliberately hide, but (as mentioned in the article) they can vary dramatically in how visible they are to us over time if, for example, they have a highly eccentric orbit.

[mnky9800n]

Show me a measurement that doesn't come with bias

[Bootvis]

I have one apple.