Yes, there are differences in ASA and utilization between small and large call centers, but one has to be careful how the question is phrased.
For the SAME call volume, the larger call center will show faster ASA because there is a greater probability that there is a free agent to take the call. Your can figure it out intuitively without any queuing theory. If the number of agents relative to the number of calls (considering AHT etc.) is VERY large, there is a very high likelihood that calls will be answered after a short delay, even during peak traffic. As you reduce the number of agents the likelihood of this happening decreases.
It gets confusing when talking about utilization (occupancy rate). We feel that if we staff optimally (relative to the call volume), the utilization should be independent of the size of the call center.. We also know that as we add agents beyond the required number (i.e. we overstaff), the utilization decreases, because there are more free agents at any point in time. So intuitively we assume that the more agents there are the more idle time they have and therefore the lower the utilization rate.
It turns out that larger call centers have higher utilization. In other words, in two call centers, each staffed to meet the same service level target, one handling a high call volume and another a lower one, the larger call center will show higher utilization. In a large call center there are many queued calls waiting to be serviced, and there is a greater likelihood of assigning a new call as soon as the agent becomes free. In a small call center the density of the calls is lower, fewer calls are queued, and the agent may wait longer for the next call to arrive.
It is important to remember that calls do not arrive in a steady pace. They arrive according to Poison process, which drives this statistical behavior (see more at
http://www.DiagnosticStrategies.com/...c_modeling.htm)
I hope this helps.
Joe Barkai
www.DiagnosticStrategies.com