Labor Day weekend at the Bourne Bridge has nothing on New Year's in China, when 130 million migrant workers leave the cities to visit their families in the sticks. It's the largest human migration in the world, according to one of the rare title cards in first-time director Lixin Fan's deceptively minimal documentary. Fan focuses on one family, the Zhangs, who like so many others are split up, with the parents laboring in a textile factory while the kids live with grandma in a village a thousand miles away. For 16 years, the parents have made the annual trip back home, and they always remind their teenage daughter, Qin, of how much they've sacrificed so she can go to school and have a better life. But then Qin quits school and starts working for herself, and the next year's reunion is a rocky one indeed. As in the recent Sweetgrass and Alamar, Fan constructs a narrative from carefully observed reality that discerns individual pathos within the sweep of history.