It's the currency of choice for tooth fairies and grandparents, panhandlers, migrant laborers and off-the-books household staff.

FORBES: The Myth Of The Cashless Society

When he saw those migrant laborers, maybe he was thinking about their wages but he was also thinking about his supper.

NEWYORKER: Out of the Office

This, Navalny argues, keeps migrant laborers in the shadows and without basic rights, and is also a major source of friction.

NEWYORKER: Net Impact

But the migrant laborers I talk to seem to accept this inequity unquestioningly, pointing out that they still earn more than they would tilling their fields.

NPR: The End of Agriculture in China

Boarding for migrant laborers is usually free--often a spot on the farmer's veranda or in a shed with fertilizers or on a rooftop, next to the drying cotton.

FORBES: Child Labor