"Joel's claim is basically that "great" developers won't have that many jobs compared to "bad" developers because companies will try to keep "great" developers.

"Joel's claim is basically that "great" developers won't have that many jobs compared to "bad" developers because companies will try to keep "great" developers. " This is a not what Joel said. Joel said that great developers are not on the market very often. They don't need to go on the open market to find their next job.