Between January and November of 2016, $24.6 billion flowed back to the pockets of Mexicans from friends and relatives living overseas, according to Mexico's central bank. That's even higher than what Mexico earns from its oil exports -- $23.2 billion in 2015. And almost all of that cash comes from the U.S. The average remittance from Mexico is about $300. Essentially, Mexico's most lucrative natural resource are the people who leave home. More from CNN Money here> Trump threatens Mexico's biggest cash source