The study looked at how big banks can save money by getting bigger, but not too big. They used a special math formula to figure this out. They found that big banks save money as they grow, even beyond $1 billion in size. But having a big variety of products doesn't always save money. Some products work well together, but others don't. This means smaller banks can get better at saving money by getting bigger, but not all banks need to be huge to be efficient.