Today, remittances are the largest, fastest-growing and most reliable source of income for developing countries. Poor nations reported $167 billion in receipts from overseas workers last year, according to the World Bank, more than all foreign aid. Including unrecorded transactions, the bank estimates that the total exceeded $250 billion.
...Mexico's annual remittance inflow has doubled since 2002 and reached $20 billion last year, second only to petroleum as a generator of wealth for the country.
Other developing nations also depend heavily on their migrants' money. Brazilian laborers in Japan send home more than $2 billion a year, out-earning their country's coffee exports. Remittances bring in more than tea exports do in Sri Lanka and tourism does in Morocco. In Jordan, Lesotho, Nicaragua, Tonga and Tajikistan, they provide more than a quarter of the gross national product.
Here is one scenario  of what the aid industry might look like in 2030 if remittances continue to grow.