it's reported by mary kay magstad, china correspondent for p.r.i.'s "the world." >> reporter: china's people are on the move. from the countryside to the city, hundreds of millions are coming in search of a better life, in the biggest migration in human history. more than half of chinas 1.3 billion people now live in cities. in 20 years, it may be two- thirds. as china's economy has grown, it has transformed lives and diets. and that's especially true, when it comes to meat. this is ms. xiong, a beijing meat seller. she grew up in a village in one of china's poorest provinces. >> when i was young, my family could only afford to have pork once or twice a year. we were poor, and our clothes were covered with patches. >> reporter: she says things got better when the family started raising pigs, instead of just working in the fields. over the past 30 years, meat consumption per capita has quadrupled, and city-dwellers eat twice as much meat, on average as those back in the countryside. pork reigns supreme. china both produces and consumes about half the