In the 20th century, the color line was the primary challenge. In the 21st century, the problem is the border line. Today, there are more people living outside their countries of birth than at any time in history, and international migrants now make up the equivalent of the world's fifth most-populous country -- just after China, India, the United States and Indonesia.
As a result, migrant-receiving nations, particularly those in the First World, are scrambling to devise strategies to incorporate and… more