To pool or not to pool in call centers

Should we pool or not? This is a question of general interest for call center management. The general perception seems to exist that pooling is always beneficial either in terms of performance (mean waiting times and service levels) or agent capacity savings. This paper aims to show that also at practical call center level a more detailed answer is in place, which may even show the opposite. To this end, it will provide 1) insights and approximate formulae, 2) numerical support and 3) general conclusions. The orientation of the paper is threefold: instructive, practical and research-oriented. An instructive approach will be followed based upon: - standard queueing results and insights, - instructive examples and - numerical results. For practical call center purposes extensive numerical results and figures are given for the generic situation of pooling two agent groups of realistic orders. These include figures for practical usage. It is also argued and numerically illustrated that an improvement of both the unpooled and pooled scenario can be achieved by overflow pooling. This in turn will lead to a variety of options for an optimization search, which is still highly open for scientific research. As such, the results are aimed at both call center practitioners and management scientists.