 Over fifty million people cross the border each year between Tijuana and San Diego, giving the region the busiest land-border crossing in the world.Since the implementation of the North American Free Trade Agreement (NAFTA) in 1994, San Diego–Tijuana has become a dominant commercial center in the United States and Mexico.The economic success of globalization has allowed San Diego–Tijuana to grow to the third richest region in the former Californias region, with a GDP of $136.3 billion in 2002.