The Orion Nebula

Can someone explain how money is generated in a colony. I don't think I've seen this in any guide. It seems that Spaceports don't do much unless the colony has everyone building trade goods.

1 pop generates 1 BC (unless you have +/- BC racepick). Spaceport increases income by 50%, Planetary Stock Exchange - 100%, also morale bonus is added to money.... More pop = more money