Viewed from the West, Mali and Nigeria are both poor. In fact, Mali is much poorer: its gross national income per head is barely one-quarter as high as Nigeria’s. The people who leave Mali in search of work seldom make it far. Most of the remittances sent to the country come from elsewhere in west Africa, although some come from France—the former colonial power. By contrast, wealthier Nigeria has a large diaspora that is spread across the rich world. They send the big bucks.
Source; The Economist