Our results must however be considered cautiously because the experi- ment does not explore all the complexity of the market. For example, the question of different vintages is not considered here. The allowances of dif- ferent vintages can be sold in separate auctions or in simultaneous ascending auctions. In our model, the product market price is fixed. However, depend- ing on the activity sector of the firms, the cost of the permits could be trans- ferred differently to the downstream product prices. Then bidders could adopt different strategies in the auction according to the market structure. Furthermore, we do not introduce forward markets in our analysis. Further research will consider these issues.