That's my problem with karma, so many people being born and huge populations on earth already, if I were going to believe in karma, then would take it further, probably have to be reincarnated on another planets or universe, as its getting a bit crowded here.
And does one regress? Maybe if we have been very very bad? Just in case karma is real, I think it best to be on good behavior, no cussing and stuff -- unless I have a very good reason.