  We study self-organized models for information transmission and herd behavior
in financial markets. Existing models are generalized to take into account the
effect of size-dependent fragmentation and coagulation probabilities of groups
of agents and to include a demand process. Non-universal scaling with a tunable
exponent for the group size distribution is found in the resulting system. We
also show that the fragmentation and coagulation probabilities of groups of
agents have a strong influence on the average investment rate of the system.
