Performance indicators for call centers with impatience

An important feature of call center modeling is the presence of impatient customers. This article considers single-skill call centers including customer abandonments. A number of different service-level definitions are structured, including all those used in practice, and the explicit computation of their performance measures is performed. Based on data from different call centers, models are defined that extend the common Erlang A model. It is shown that the proposed models fit reality very well.