"The last decade or so has witnessed an unprecedented pace of bank mergers and acquisitions. In the United States, Brewer et al. (2007), for example, document that between 1990 and 2004, the number of bank mergers and acquisitions (M&As) averaged about 435 per year compared to 345 per year over the period 1980–1989. As a result, the number of banks operating in the United States has declined by approximately 40% since 1990." (Quoted from paper)