This book contributes substantively to state-of-the-art macroecomic modeling by providing a method for modeling large collections of heterogeneous agents subject to n-pairwise externality called field effects, i.e. feedback of aggregate effects on individual agents or agents using state-dependent strategies. Adopting a level of microecomic description which keeps track of compositions of fractions of agents by 'types' or 'strategies', time evolution of the microecomic states is described by (backward) Chapman-Kolmogorov equations. Macroecomic dynamics naturally arise by expansion of the solution in some power series of the number of participants. Specification of the microecomic transition rates thus leads to macroecomic dynamic models. This approach provides a consistent way for dealing with multiple equilibria of macroecomic dynamics by ergodic decomposition and associated calculations of mean first passage times, and stationary probabilities of equilibria further provide useful information on macroecomic behavior.