[thedufer]

We allow people to trade futures i.e. the next of a particular resource they get must be handed over. This means that they don't clear within a turn, but leads to interesting economics - you can trade away risk, usually at a significant cost. Its easy to avoid conflicts - if you've already traded your next wheat, you can't trade it again until you get one (but you could, for instance, trade your 2nd future wheat).