The article talks about how waves of mergers between companies that operate at different levels in the same industry can sometimes harm competition. To tackle this issue, they suggest that stopping a merger that removes the final independent supplier in an industry might be best. This type of merger could make competition worse, especially when there are lots of companies selling the final product and not many that provide the raw materials. The effects are more likely to be negative when contracts between the two types of firms are set up in a specific way. However, having the right rules against mergers can change depending on how well the companies work together or how different their products are from each other.