longpasa said:
Trade investment +30 is the effect of a event that fires. Shortly after colonizing your first province, you get an event about what to do with the natives. You must have chosen "Trade with them" (don't remember the exact wording). This will fire the "Lucrative Trade" event that gives a +30 gc investment in trade tech for x number of months. I have never had more then 3 at the same time, so the number you have is just insane!