Nanban Trading-Backstocks and Town Status

EA towns go through many different Town Statuses in a day. Most offer bonuses to certain trade goods except a Recession which will penalise all trade goods you might want to trade, it's best to avoid trading in a town currently in a recession. The UWODB nanban section displays all the town status and what their effects are such Festival (bonus to Alcohol / Foodstuffs / Luxury Good). 

Town Statuses are more important if you are nanban trading without the NC Nanban Purveyor Certificate items.

You can check the status of any towns you have unlocked from any Nanban Trade Merchant or by opening your port permit map and moving the cursor over the EA towns.

Next to look at 'Backstock'. To make an example backstock is like a warehouse, the more firearms they have in stock for example, the less they want firearms, but they will offer you more firearms for a trade.
Looking at backstock graphs you want to trade your goods that are low on the graph, and receive goods that are high on the graph, but with the NC Nanban Purveyor Certificates this is also easier. Below are an example of what you should be looking for when making a trade, such as trading Saltpetre(ores) in Hangzhou which is a good trade for Wuzu Porcelain(crafts)

Here we can see the 'Ores' very low on the graph which is what you want when trading Saltpetre.

Here we have 'Crafts' that are reasonably high, still with the Nanban Purveyor Certificate you will receive 1:1 ratio on goods. And hopefully if you have unlocked Wuxu Porcelain you will be able to trade for it.

Check UWODB nanban page for additional backstock info, each town has a different backstock base, such as Hangzhou have a very low backstock base with ores. To make an example again using a warehouse scenario, the warehouse at Hangzhou empty their ores cache quickly, so they're always in need of ores. 
Below is an example if you click on South China-backstock, scroll down to Hangzhou you will see highlighted in green the Ores at -3 in most town statuses, this good if you want to trade Ores, bad if you want to receive ores. Highlighted in yellow is the Crafts with +1 which is good for receiving crafts such as Wuxu Porcelain.

You can click on a country's backstock to check if you will make a successful trade in a town with a certain type of good such as alcohol, arms, ores, wares etc, but you must check to see if that country will pay you well for a particular good. For example, Japan backstock for alcohol is -1/-3 which is good, but they won't pay you well for many alcohols. Wine is the best by far, so the high value wine offers plus Japan's -1/-3 backstock on alcohol make trading wine in Japan very profitable. Same can be said for trading Saltpetre in Hangzhou.

Looking at the table above, you will see Ores at -5 under the 'Boom' column. Boom is a town status that will drop backstock on all goods, but you will still make not only a great trade, but also receive a much larger ammount of Culture Contribution points in order to unlock another town to trade in or higher value trade goods.

Market Rates:


Clicking on 'Market rates' you will see a list of the trade goods asociated with the country you're trading in. For example if you want to trade your goods for Wuxu Porcelain and would like to know where to sell and how much you should be looking for you can check, see the picture below:

 

Here you can see I have moved my cursor over 1 of the town images and it says 'The British Isles', under this column we can veiw what Chinese goods will sell for, so we can see Shaoxing wine, Chinese tea and Wuxu porcelain selling best in the British Isles and that Wuxu Porcelain will get you a very high price(highlighted with a red star). The Huzhou Brushes sell best in Iberia, you only need to move you cursor over the town image, or yellow/red star and you will notification telling you the area.

Next we'll look at receiving gifts from nanban trading.