I've been testing it, and I can't seem to increase my income or any other indicators when I spam high elf nobles. Going from 0 to 5, my income decreases by the upkeep of each new noble exactly, which implies that I'm not actually making any new income. I currently have far too many trading partners and am trading 100% of each trade good, so I should be able to increase my trade income with the nobles increasing my quantities of trade goods, but there isn't actually any income increase. I have them all in the same province, and even the same region as a trade good producing building, and I still show 100% of each trade good being traded, but they don't actually seem to generate any income whatsoever. Is this a known bug?