I'm playing Egypt, and recently took Godwanaland, or whatever its called, just south of Cairo. But the merchants I have trading the ivory earn wildly fluctuating incomes, and I'm not 100% sure why. Like one turn it will be 22 F, then 100+ F, then back to 22F again for a few turns, and now its 300+ F. And the whole time he's been a level 5 merchant. One thing which seemed to make it drop was when I built a port. One thing that seemed to make it go up was when I moved the capital from Acre to Cyprus. But that doesnt explain all of it. Like a few turns after I built the port and it dropped from 100+ to 22, it went back up to over 100 again. I never saw this kind of thing in previous games.