Migration is one of the most important changes now roiling African village life. To study that phenomenon and its impacts, Joachim De Weerdt and Kalle Hirvonen have been following a sample of 6,353 people in the remote Kagera region of Tanzania since 1991. When they last interviewed them in 2010, they found that more than half of those living had left their home villages. Migration, in fact, has been the principal pathway out of poverty: migrants economically outperformed those staying put by far, even after taking age, gender and other characteristics into account (see here, here and here). On average, they had become twice as rich as those they left behind despite starting out from very similar conditions.