Successive chapters on social class, neighborhood, ethnicity, gender, and social networks delineate the leaders of linguistic change as women of the upper working class with a high density of interaction within their neighborhoods and a high proportion of weak ties outside of it. Detailed portraits of individual leaders show that the women who lead linguistic change are distinguished from others by their general pattern of deviation from established norms of conformity. Mathematical models are developed to account for the linear incrementation of change in progress, and the transmission of change across generations.