A sign on the border between San Luis Río Colorado and Nogales, Sonora. Illegal Mexican immigration to the United States has plummeted in recent years, with Central Americans now representing the largest group. Illegal immigration remains steady, but for the first time in decades there are more Mexicans leaving the United States than coming in. The Great Recession north of the border and the decrease in demand for low-wage workers in agriculture and construction have been leading factors. Mexico’s economy and the middle class continue to expand as well, with the Mexican government investing more in schools and manufacturing at home to create an educated populace with more opportunities. The OECD (The Organization for Economic Co-operation and Development) and WTO (The World Trade Organization) both rank Mexican workers as the hardest-working in the world in terms of the amount of hours worked yearly.