[Bring_Back_Shantz]

Originally Posted by arsenal

It's not like playing the lottery. Objects in space have an orbit, and a path. It's only a matter of time until a NEO and Earth's path's cross. If you can find the path of a NEO, you can then calculate if and when that object and earth's paths will cross (given that nothing deviates that objects orbit).

Okay,
But based on a few assumptions:

1) we don't know about the vast majority of the objects in our solar system
2) we don't know about their orbits
3) The are relatively randomly arranged

then we can treat it as any other random event.
On aveage a object of X size hits the earth every 1000000 years.
So the chances of one hitting this year are 1 in 1000000, regardless of how long it's been since the last one hit.