Above in this thread I briefly modeled some transactional data for cities and concluded that demand for goods in a city was about 80gp per family. I then did some further estimates that if all trade was done in the city, total transaction value might be 250gp per family.
With further refinement (via spreadsheets too complex to share here):
- the demand for goods is 75gp per family
- the total value of all market transactions is 100gp per family*
- The absolute maximum number of merchants available is 36 times the average number listed on the Markets and Merchants table.
*There are more transactions than the demand for goods from just the urban families because some transactions occurring are by peasants from the surrounding area, church leaders from tithes, etc.
This leads to the following maximum monthly volume:
Class I: 30 Large Ships, 90 Small Ships, or 45 30-horse Caravans
Class II: 7-8 Large Ships, 22 Small Ships, or 11 30-horse Caravans
Class III: 3-4 Large Ships, 11 Small Ships, or 6 30-horse Caravans
Class IV: 1 Large Ship, 3 Small Ships, or 2 20-horse Caravans
Class V: 1 Small Ship or 2 10-horse Caravans
Class VI: 1 10-horse Caravan
I probably need to create an NPC specialist class called an “agent” “broker” or “procurator” who can conduct dealings on behalf of PCs so that PCs who end up owning, e.g., 8 Large Ships can use brokers to handle their trade.