[Off topic] There is a populist discussion going on in the comments of the original post. I did a lot of strategy work in banking mergers and there are different ways to look at the concentration in an industry. The top level player count is an easy statistic, but what is more relevant is the choice that customers (especially small businesses) have on the ground. How many different bank branches are within a 10km range at any point in the US? If there are 30 banks, but each concentrate on a specific state, then the market looks very competitive, but on the ground, customers face a monopoly. On the other, if all 4 banks are represented in most small villages, the market could be competitive.