Jon Purizhansky from Buffalo, NY says that various geopolitical events have historically driven migration trends, such as that when the United States and Mexico signed the North American Free Trade Agreement (NAFTA) in 1994, government-subsidized corn that was cheaply produced in the U.S. began to flood the market in Mexico. With this new influx of artificially under-priced corn, farmers in Mexico could no longer afford to make a living growing corn.