Quick rundown of the bonuses
100M 5%
500M 10%
1B 20%
2B 30%
3B 40% etc. up to 8 or 9 billion
These apply to production and construction.
Happiness bonuses (production only)
Rioting -100% (no production or construction at all!)
Angry -20%
Unhappy -10%
Indifferent 0%
Happy 10%
Jubilant 20%
The happier your population, the faster it will grow, so it behooves you to get 'em happy.
Kim