CALL CENTERS (CENTRES) - Faculty of Industrial Engineering and ...

Introduction †
Call center is the common term for a telephone-based human-service operation. A call center
provides tele-services, namely services in which the customers and the service agents are remote from
each other. The agents, who sit in cubicles, constitute the physical embodiment of the call center.
With numbers varying from very few to many hundreds, they serve customers over the phone, while
facing a computer terminal that outputs and inputs customer data. The customers, possibly up to
thousands at a given instant, are only virtually present: they are either being served or they are
delayed in, what we call, tele-queues. Those waiting to be served share a phantom queue, invisible to
each other and the agents serving them, waiting and accumulating impatience until one of two things
happens – an agent is allocated to serve them (through a supporting software), or they abandon the
tele-queue, plausibly due to impatience that has built up to exceed their anticipated worth of the
service.
Contact centers are the contemporary successors of call centers. In addition to phone services,
they interface with customers via the internet, email, chat and fax. Call or contact centers are the
preferred and prevalent way for many companies to communicate with their customers. (Fortune-500
companies are estimated to operate, on average, 30 call centers each.) The call center industry is
thus vast, and rapidly expanding in terms of both workforce and economic scope. For example, it is
estimated that 70% of all customer-business interactions occur in call centers and that $700 billion in
goods and services were sold through call centers in 1997. These figures have been expanding 20%
annually. Three percent of the U.S. working population is currently employed in call centers. This
amounts to 1.55 million agents, and some estimates actually go up to 6 million.
The modern call center is a complex socio-technical system. Some view call centers as the business
frontiers but others as the sweat-shops of the 21st century. Either way, within our service-driven
economy, telephone services are now unparalleled in scope, service quality and operational efficiency.
Indeed, in a large best-practice call center, hundreds of agents can cater to thousands of phone callers
per hour; agent utilization levels can average between 90% to 95%; no customer encounters a busy
signal and, in fact, about half of the customers are answered immediately; the waiting time of those
delayed is measured in seconds, and very few abandon while waiting.
The design of the modern call center, and the management of its performance, surely must be based
on sound scientific principles. This is manifested by a growing body of academic multi-disciplinary research,
devoted to call centers, and ranging from Mathematics and Statistics, to Operations Research,
Industrial Engineering, Information Technology and Human Resource Management, all the way to
Psychology and Sociology. My goal here is to “describe” this research through a list of abstracts, as
complete and updated a list as possible. The abstracts originate in papers that are either directly
related to or have been judged potentially helpful for academic research on call centers.
† The text is adapted from “Empirical Analysis of a Call Center”, by A. Mandelbaum, A. Sakov, S. Zeltyn, Technion
Technical Report, 2001; and from “Introduction to Mathematical Models of Call Centers”, preprint by G. Koole and A.
Mandelbaum, 2001.
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