The good news, in the last twenty years we’ve not only recognized the need to look for asteroids that can hit Earth, but we’ve probably found about 93% of the ones that are at least one kilometer in diameter. The bad news is that asteroids as small as 140 meters can cause massive damage, there are possibly tens of thousands of them, and the searches are running into financial and logistical problems. And then there are the asteroids that are more than 40 meters across, which are enough for regional damage. The estimate is that only 1% of them have been found and that there are millions. The search continues. We’re making progress. And we won’t know if we can never know if we are working fast enough.
(Click on the chart for the link.)