What volume of goods does a settlement trade in?

I've wondered this for a while, but never gotten around to asking. Obviously the core rulebook has rules for how many merchants are willing to trade with you and what volume of goods they have. But I was wondering if there is a method for deciding what volume of a particular good an entire settlement will trade in over a given time period? Has anyone attacked this problem?

the short answer is that yes, this has topic has been addressed, but I couldn't find the existing thread to link you.  There's also a fair bit written about coin & commerce in the 3rd issue of Axioms.