State variable

The specific values chosen depend on why we want the information. In system dynamics modelling, state variables are the stocks (levels or accumulators) in our models. Unlike rate variables whose values return to zero when the simulation of a model is halted, state variables retain their values. In this way they represent the extant state of the problem being simulated. In system dynamics modelling, a defining test of a variable being a state variable is that when flows stop, state variables hold their value. Also see variable, order.