Figure 6.

Independent departure symmetry follows from independent list symmetry. Consider a system with independent list symmetry (within the dashed box). Departures of single jobs from this system can be placed into an auxiliary departure queue that keeps track of the last several departures. Independent list symmetry is also preserved in the departure queue, owing to the arguments figure 3 and appendix B. Since this queue is an independent list, it is reasonable to believe that the probabilistic process for the substrate class of departures is a sequence of independently but identically distributed random variables. (Online version in colour.)