Every day, thousands of Africans living abroad line up in money-transfer offices to wire home the odd dollar they are able to save. From the US, Saudi Arabia, Germany and Belgium - the top sources of remittances to developing countries - the total of money sent is more than foreign development aid. Yet most of the money sent home by migrants is unrecorded, and therefore does not enter many countries' national statistics. Development planners increasingly stress the importance of tracking this money. That could help governments try to increase remittances as a source of development finance and better channel them into productive sectors.