Hi, I really want to play this game properly, without cheating lol, but I'm having trouble understanding approval rating.

I just started a new immense, tough game, with a custom race using Altarian tech tree with maxed morale and loyalty attributes. I have about 10 colonies right now and most are at 90-100 percent approval with maxed population and not much structures, just the basics. My homeworld however is at 40% and falling. the main difference between my HW and colonies is that I have the population cap upgraded to about 20b and most tiles filled, where as my colonies are all at the standard 8b cap. I have probably 1/4 of the tiles on my HW with morale boosting structres and still the approval rating is falling.

So my questions are; is it just overpopulation? What are the consiquences of a low approval rating, will colonies rebel? What kind of approval should I be aiming for with my colonies? Does a colony's approval go down as population grows?

I'm so confused.

EDIT: nevermind, wiki just answered my questions.