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

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Abstract. This paper models the cross-selling problem of a call center as a dynamic service
rate control problem. The key tradeoff between revenue generation and congestion in a call
center is addressed in a dynamic framework. The question of when and to whom to cross-sell
is explored using this model. The analysis shows that unlike current marketing practice which
targets cross-sell attempts to entire customer segments, optimal dynamic policies may target selected
customers from different segments. Structural properties of optimal policies are explored.
Sufficient conditions are established for the existence of preferred calls and classes; i.e., calls that
will always generate a cross-sell attempt. Numerical examples, that are motivated by a real call
center, identify call center characteristics that increase the significance of considering dynamic
policies rather than simple static cross-selling rules as currently observed. The value of these dynamic
policies and static rules are compared. The numerical analysis further establish the value
of different types of automation available for cross-selling. Finally, the structural properties lead
to a heuristic that generates sophisticated static rules leading to near optimal performance both
for a loss system and a queueing system.
Keywords: Call center, Cross-selling, Revenue management, Customer relationship management,
Dynamic control, Loss system
153. Sisselman, Michael E. and Ward Whitt. Value-based routing and preference-based routing in
customer contact centers. Working paper, 2005. Also: A preference-based-routing example
solved by linear programming with excel solver. Supporting material, 2005. Available at:
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Abstract. Telephone call centers and their generalizations—customer contact centers—usually
handle several types of customer service requests (calls). Since customer service representatives
(agents) have different call-handling abilities, contact centers exploit skill-based routing (SBR) to
assign calls to appropriate agents, aiming to respond properly as well as promptly. Established
agent-staffing and call-routing algorithms ensure that agents have the required call-handling
skills and that constraints are met for standard congestion measures, such as the percentage of
calls of each type that abandon before starting service and the percentage of answered calls of
each type that are delayed more than a specified number of seconds. We propose going beyond
these traditional performance measures to focus on the expected value accrued from having
the agent handle the call. Expected value might represent expected revenue or the likelihood
of first-call resolution. Value might also reflect agent call-handling preferences. We show how
value-based routing (VBR) and preference-based routing (PBR) can be introduced in the context
of an existing SBR framework, where the existing SBR is based on static-priority routing
using a highly-structured priority matrix. Since VBR and PBR use the same SBR framework,
they can be implemented with the existing SBR algorithm in the automatic call distributor
(ACD); it is not necessary to replace the ACD. We use mathematical programming to find an
effective priority matrix. We select the priority matrix to use during a specified time interval
(e.g., 30-minute period) by maximizing the total expected value over that time interval, subject
to constraints that ensure that standard performance constraints are met.
Keywords: Customer contact centers, Telephone call centers, Skill-based routing, Value-based
routing, Preference-based routing, Indirect value-based routing, Priorities, Mathematical pro-
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