Is this a good time to be a small credit union? Not everyone thinks so. Maybe for good reason. Between 2009 and 2015, the three largest banks in the country grew deposits by $1.27 trillion, while the remaining 11,000 U.S. banks and credit unions generated $1.84 trillion. In other words, the top three grew by an average $423.3 billion each, while other financial institutions (FIs) averaged just $167.3 million.