The second most spoken language in Mexico, however, is English. It is used extensively at border areas, tourist centers and large metropolitan areas, a phenomenon arguably caused by the economic integration of North American under the North American Free Trade Agreement (NAFTA) and the immigration phenomenon and the return of workers and their families from the United States. In border cities, American TV and radio waves in English (and Spanish) are received as much Spanish-speaking radio and TV stations from Mexico on the US side of the border, thus a bilingual cross-cultural exchange is at work.