Chat with merchants should reveal surplus/deficit for directly connected regions

[Azerax]

What about adding the players Trading skill into the equation?  Let's say the base accuracy of the information is 50% (a new trader doesn't have that many connections)
So, for this example, the trading skill goes from 1 to 100

The accuracy would be 40% + (trading skill / 2)

That would give a range of 40% to 90%

So, with regions with 1 granary, the result would be (based on the granary being full)
"Oh, the granary is pretty empty" to "I was in the granary yesterday and it was pretty much full"

The idea is that Traders build connections the more they trade, and since all they have to do is trade to build it up, it won't exclude anyone who is serious about trading.

[Indirik]

The more ways to use trading skill, the better.