Economics, part 7: Middle Men(part 1)

This is the part where we start to involve merchants and teamsters. They play a rather massive roll if your campaign setting has them. This is the first point in our little model where non-producers show up. It's also likely the first time in our model where money is used in the vast majority of transactions as opposed to barter between goods/services.
Today's post is going to be about Closed Economic Models. What this means is that there is no trade coming from outside the region you've already developed thus far to throw off our numbers. I'll deal with an Open Economic Model in a later post.
We've already determined the Base Cost Value(BCV) of our secondary products. We've also already determined what every person in our model needs in terms of supplies to survive at our "baseline" of 626 cp per year. Please note, the BCV is NOT a measure of actual monetary value. It's a measure of amounts produced if all things were created and sold equally based on amounts, skill, and time. It's a simplification so we're not talking in bushels of different crop types and pounds of different ore types.
Because of where we are in this series of posts, for the time being we'll only concern ourselves with the BCV of secondary products* and I'll expand accordingly in later posts. First, you're going to need to figure out the total amount of a given secondary product by quality. This can be decided however you want to handle it, but given that we've already made some die rolls, you can use the 20+ point quality scale(which got partially cut off by blogger) used to create the secondary product and see which areas of your region are more likely to be known for better quality secondary products. Using this knowledge, you may start making a chart showing where each source of secondary product is and see which areas have a lack.
Once the chart is finished and you have a pretty good idea of what resources a community has, you then have to determine what's actually for sale. Not everything a community produces will be available for trade. How you determine this is up to you but under normal conditions, I usually have 75+1d20% available for trade.

Next time: Determining Demand.

* The reason for not doing this for the step between primary production and secondary production is two fold:

• In the models I'm using, the relationship between primary and secondary producers is a mostly stable and direct one. A primary producer will tend to "feed" a secondary producer year after year, and the rates of exchange will tend to remain the same within reason. While there would be a certain amount of horse trading going on between the two, there's going to be a more closely tied relationship between a primary and secondary producer than there is going to be between any producer and a middle-man.
• I had not yet written or even thought out this part of the series any more seriously than "I think I'll need a post on Supply and Demand at some point. Maybe when I talk about merchants."