The States With The Highest Percentage Of Native-Born Residents

My theory on northern Idaho is that it is a thin strip of state between two other states. If people are likely to live and die within 1-hour of where they are born (let's say the hump of the bell curve is one hour), then that strip is going to get a fair number of people from the two states on each side.

I wonder if you can correct this map to discount people who moved across state lines, but did not move more than 1-2 hours from their place of birth.