I am commencing a study of the dynamics of language survival and extinction, focusing primarily in the social precursors and conditioning factors. There appears to be little work on explicit modelling the dynamic behaviour of language systems in this way which is surprising since the interactions of, for example exogamy and social/economic factors are clearly important. There is work in mathematical sociology but it concentrates on the grammatical aspects, taking an evolutionary view. Does anyone know of any qualitative or quantitative system work in this area?