 Studies show that the elimination of barriers to migration would have profound effects on world GDP, with estimates of gains ranging between 67–147%.According to Branko Milanovic, country of residency is by far the most important determinant of global income inequality, which suggests that the reduction in labor barriers would significantly reduce global income inequality.A study of equivalent workers in the United States and 42 developing countries found that "median wage gap for a male, unskilled (9 years of schooling), 35 year-old, urban formal sector worker born and educated in a developing country is P$15,400 per year at purchasing power parity".