Item creation?

Are items created in game or is there a limited supply of everything in game? Like the number in circulation, is that number fixed or do countries create items for trade?

items are taken into and out of the game fairly often.

some items are generated daily throughout pretty much all aspects of the games (crime, city shops, country stock, caches, jobs, etc) and some are limited. 

Overseas items are replaced some time after they sell out. That time is determined by the time it took for them to sell out.

City stores will also replace stock that has sold out after some time. I am not sure what their restocking time is based upon.

So, all stock in stores will be replenished over time. Demand for some items, especially consumable items is greater than demand for other items, such as souvenirs.

Consumable items are removed from the game when they are consumed. The only way that non-consumable items are removed from the game is by selling them to one of the stores in the city.

Other items are created and found by doing various crimes. Crime results can be random but certain crimes will have a specific group of items related to that crime and quite often, those items will not be available anywhere else, except for when they are being sold by a player.

There are some other ways to get items, such as finding items in the city, finding items during special events (such as Halloween or Christmas) and getting items from NPC fights.

New items are being created all the time, some are worth a lot more than others. Knowing the value of items is a big part of the game, so it pays to learn what is what, and check market prices often, so you can get the most out of the items you collect.