It doesn't need to square with it. In some places population can increase, in others it can decrease; add them all up and there is some number, ΔP, that is eit

It doesn't need to square with it. In some places population can increase, in others it can decrease; add them all up and there is some number, ΔP, that is either positive or negative. For a long time now, it's been an exponentially-increasing positive, which I contend is bad news, and I hope it reverses. If people move around, all that does is move the growth around.