Six large firms dominated the sale of seeds and agricultural chemicals in 2015 in the United States and around the world: BASF, Bayer, Dow Chemical, DuPont, Monsanto, and Syngenta. The “Big Six” produced and sold crop-protection products such as pesticides, herbicides, and seed treatments. Each firm supported its products with major investments in research and development, leading to improvements that have been an important source of growth in agricultural productivity. In 2015 and 2016, three mergers were announced, encompassing five of the six firms. These mergers led to extensive antitrust reviews by enforcement agencies in the U.S., the European Union, and other countries, with adjustments to the mergers before they were approved.