This study looked into how mergers between companies that operate at different stages of production affect their ability to work together to charge higher prices. They found that when companies merge in a way that covers different production stages, it can make it easier for them to collude and raise prices on the customers they sell to. The research shows that when merged companies are also able to punish those that don't follow the agreement, it makes it even more likely that they will cooperate to increase their profits. So, when companies in an industry are separate, merging their stages can help them work together to raise prices on their customers.