The United States is a world leader in pharmacology, constituting the largest market for pharmaceuticals in the world, and also a key global player in pharmaceutical research, production, and sales. Five of the ten largest pharmaceutical companies in the world, as of 2014, are based in the United States: Pfizer, Merck & Co., Eli Lilly & Co., Abbott Laboratories, and McKesson. Unlike many countries, the United States does not have general price controls for pharmaceuticals, although individual insurance plans may negotiate prices with their suppliers, and some government agencies, such as the U.S. Department of Veterans Affairs, also negotiate the price of pharmaceuticals.