summary - the risk from larger asteroids of 1 km upwards, large enough
to have some global effects is more or less retired as a result of
astronomical searches for the last few decades. There is still a risk
from smaller asteroids, but in most cases we’d be able to deflect them
if necessary, or evacuate the area. The chance of dying from an
asteroid is tiny, far less than the risk of dying of lighning.
20 - 40 METER ASTEROIDS ARE TINY - JUST
LARGE ENOUGH TO GET THROUGH THE EARTH’S ATMOSPHERE
asteroid 20 meters in diameter hits every 80 years or so. Since only 1%
of the Earth is urban that means around 8,000 years between impacts on
an urban area.