Money in Catan

One of the people that I play Settlers of Catan posed the question on whether one could introduce gold as money, not any of the gold variants in the expansions, into the game so that people actually use it to trade with. This would remove one common friction to trade, namely there won't have to be a double coincidence of wants. In addition, it would serve as a good economics lesson on how money works, despite being inherently valueless. Unfortunately, I don't think it is possible to graft money onto Settlers in a way that makes prices endogenous. The structure of Settlers makes trade non-essential and any additional frictions would completely shut down trade.

Before going into detail on the issues, I would like to formalize how gold would be added to Settlers. Gold's purpose is solely to be a medium of exchange. This means that there will be nothing to buy from the game for gold, only the other players. So any gold that enters the hands of the players will never leave. As we want the players to use gold instead of relying on barter, all trades must have just gold on one side of them. To remove the loophole of players swapping gold back and forth to simulate barter, we will further restrict trades to only be the active player. Things like can more gold be generated or how much gold each player starts with can be left up in the air and isn't really important for discussing what goes wrong.

I think that most people who have played Settlers notice that the end game tends to turn into a game of solitaire. Once you have your production upgraded enough through cities and settlements, there is usually no need to trade with other people. How ever you have built will generate the necessary points to win. Even early game, trade is not essential with things like sufficient diversification in starting resources and 4:1 with the bank. This means that if trade becomes more difficult it will vanish from the game.

How difficult trade is really depends on who you are playing with. Some groups trade a lot, others never do anything that is not 2:1 or better. In the former case, trade might still exist with gold due to the high level of reciprocity already present in the group. Though there is the added layer of trust needed that people will trade back for gold on your turn, which makes trade less likely by making it more risky. Those who are already stingy traders will completely shutdown because gold is literally a worthless resource and they will not trust that anyone will trade back for gold.

In addition to the trust issues, gold is extremely undesirable in the late game. It doesn't help you to win and no one is trading, so there is no need of a resource to facilitate trade. In this way gold becomes a hot potato and anyone left with more gold than he started with is the sucker for giving up actually useful resources. I would expect that this would cause gold to hyper-inflate as the game progresses. If there is a way to generate gold, one might see trade later in the game as enough exists to pay the exorbitant prices. But in games with no gold production, trade will cease when prices exceed the available gold.

Given that adding gold to Settlers would not achieve endogenous prices, is there any game out there that we could graft gold onto to get them? While my knowledge of games isn't perfect, I would highly doubt such a game exists. Mostly because this endogenous price requirement seems like it would have to be a core game mechanic to function, not something grafted on by hobbyists. Though I do think that it is possible to create a game with money and endogenous prices. It would have to encourage or require specialization so that trade is necessary and benefits both parties. But not a cooperative game like Arkham Horror where any prices are simply mechanisms to get the appropriate items to each player. I think something like a vertical production chain or a medieval king's council could have the desired features.