Although the growing U.S.-Mexico corn trade has changed significantly since the implementation of the North American Free Trade Agreement in 1994, it retains many of its pre-trade-liberalization characteristics. The majority of U.S. corn exports to Mexico still consists of yellow corn, which is primarily used as an ingredient in animal feed. From 1998 to 2002, the United States also exported to Mexico substantial quantities of white corn, which is used to make tortillas, but these exports have since diminished, possibly due to Mexican Government support for domestically produced white corn. The number of agricultural producers in Mexico declined substantially during the 1990s, but the Mexican corn sector still features a large number of small-scale producers, whose efforts are also supplemented by government payments. Broader access to U.S. yellow corn is fostering the expansion of hog and poultry production in Mexico, while Mexico's large flour companies are increasing their role in tortilla production, not only in Mexico but also in the United States.