What is the Frequent Source of Call Center Forecasting Problems?

The major Workforce Management Systems available today use the Erlang-C model for staffing projections. There are many deficiencies when Erlang-C and the other classic queuing models are used. For example, use of the Erlang-C model results in varying degrees of overstaffing. Moreover, Erlang-C cannot be used for all of the “What if” scenarios that address information on variability and extremes because the results provided by the model are only averages of key performance measures.

Erlang-C is also based on the assumption that all calls not answered immediately are placed in queue and never leave the queue except to be answered. This means that Erlang-C cannot:

1. Predict Busies or Abandonments, and
2. Deal with overload conditions.

When the call arrival rate exceeds the capacity of agents to answer them, in reality, some calls will be Lost or Abandoned. However, Erlang-C assumes the queue will get longer and longer with time. Experience has shown that Erlang-C predicts higher Average Speed of Answer and poorer Service Level than those found in reality.