We have a good idea of how many planet-killer asteroids are out there and that we have detected 90% of them. And 100% of the extinction-level asteroids. Planet-

We have a good idea of how many planet-killer asteroids are out there and that we have detected 90% of them. And 100% of the extinction-level asteroids. Planet-killer asteroids are large, kilometers in diameter, and visible. This asteroid is 10m in diameter, way harder to detect which is why didn't detect it until last minute. The current goal of NASA asteroid detection is 90% of 150m asteroids which can cause regional disaster.