Each step of health care gives you +.1% increase in population a year.
It isn't +.1% a year. It's +.1% a month. This equates to just under 5% a year if you have all the healthcare reforms. This is why it's so OP early on. Or to put it another way, if you were in a situation (purely theoretical) where you only had healthcare giving population growth, you population would double every 12-14 years or so.