  We discuss a crowd-based theory for describing the collective behavior in
Complex Systems comprising multi-agent populations competing for a limited
resource. These systems -- whose binary versions we refer to as B-A-R (Binary
Agent Resource) systems -- have a dynamical evolution which is determined by
the aggregate action of the heterogeneous, adaptive agent population.
Accounting for the strong correlations between agents' strategies, yields an
accurate analytic description of the system's dynamics.
