Others already mentioned the impact band.

The more interesting question in pertinent scenario is whether countries will prevent asteroid deflection if it increases chance of randomly shifting impact to them by some %. I surmise no one will do anything to save someone elses ass, only their own, i.e. US saving India's ass but fragments end up over PRC and kills someone... congrats, just started WW3. Countries powerful enough to deflect, will risk fallout to avoid impact on itself... since weak suffer what they must.