I've just updated to 4.0 my growth rate is 0.01 meaning it takes 100 turns to get 1 population. I haven't played for awhile but this seems so off to me. Growth for me has come from Ideology spending and random events. Natural growth is basically useless it seems. I get the feeling that someone messed up the decimal and they meant 0.1 so 1 pop every 10 turns. As is you will never need to build cities I can't get the pop high enough.