A Practice-Oriented Overview of Call Center Workforce Planning

References

• Akşin OZ, Armony M, Mehrotra V (2007) The modern call-center: A multi-disciplinary perspective on operations management research. Production Oper. Management 16(6):665–688.Google Scholar
• Akşin OZ, de Vericourt F, Karaesmen F (2008) Call center outsourcing contract analysis and choice. Management Sci. 54(2):354–368.Link, Google Scholar
• Akşin Z, Ata B, Emadi SM, Su C-L (2017) Impact of delay announcements in call centers: An empirical approach. Oper. Res. 65(1):242–265.Link, Google Scholar
• Aktekin T (2014) Call center service process analysis: Bayesian parametric and semi-parametric mixture modeling. Eur. J. Oper. Res. 234(3):709–719.Google Scholar
• Aktekin T, Soyer R (2014) Bayesian analysis of abandonment in call center operations. Appl. Stochastic Models Bus. Indust. 30(2):141–156.Google Scholar
• Aldor-Noiman S, Feigin PD, Mandelbaum A (2009) Workload forecasting for a call center: Methodology and a case study. Ann. Appl. Statist. 3(4):1403–1447.Google Scholar
• Antipov A, Meade N (2002) Forecasting call frequency at a financial services call centre. J. Oper. Res. Soc. 53(9):953–960.Google Scholar
• Armony M, Maglaras C (2004a) Contact centers with a call-back option and real-time delay information. Oper. Res. 52(4):527–545.Link, Google Scholar
• Armony M, Maglaras C (2004b) On customer contact centers with a call-back option: Customer decisions, routing rules, and system design. Oper. Res. 52(2):271–292.Link, Google Scholar
• Armony M, Ward AR (2010) Fair dynamic routing in large-scale heterogeneous-server systems. Oper. Res. 58(3):624–637.Link, Google Scholar
• Armony M, Shimkin N, Whitt W (2009) The impact of delay announcements in many-server queues with abandonment. Oper. Res. 57(1):66–81.Link, Google Scholar
• Armony M, Israelit S, Mandelbaum A, Marmor YN, Tseytlin Y, Yom-Tov GB (2015) On patient flow in hospitals: A data-based queueing-science perspective. Stochastic Systems 5(1):146–194.Link, Google Scholar
• Atar R (2005) Scheduling control for queueing systems with many servers: Asymptotic optimality in heavy traffic. Ann. Appl. Probab. 15(4):2606–2650.Google Scholar
• Atar R, Giat C, Shimkin N (2010) The cμ/θ rule for many-server queues with abandonment. Oper. Res. 58(5):1427–1439.Link, Google Scholar
• Atlason J, Epelman MA, Henderson SG (2008) Optimizing call center staffing using simulation and analytic center cutting-plane methods. Management Sci. 54(2):295–309.Link, Google Scholar
• Avaya (2011) How to balance business goals with Avaya Business Advocate. Accessed June 14, 2023, http://www.stlcom.com/wp-content/uploads/2016/07/49_AvayaBusinessAdvocateBrochure.pdf.Google Scholar
• Avramidis AN, L’Ecuyer P (2005) Modeling and simulation of call centers. Proc. 2005 Winter Simulation Conf. (IEEE, Piscataway, NJ), 144–151.Google Scholar
• Avramidis AN, Deslauriers A, L’Ecuyer P (2004) Modeling daily arrivals to a telephone call center. Management Sci. 50(7):896–908.Link, Google Scholar
• Avramidis AN, Chan W, Gendreau M, L’Ecuyer P, Pisacane O (2010) Optimizing daily agent scheduling in a multiskill call center. Eur. J. Oper. Res. 200(3):822–832.Google Scholar
• Babat F (2015) Evaluation of service level approximations in call centers. Accessed September 6, 2020, beta.vu.nl/en/Images/werkstuk-babat_tcm235-458387.pdf.Google Scholar
• Baccelli F, Hébuterne G (1981) On queues with impatient customers. Kylstra FJ, ed. Performance ‘81 (North-Holland, Amsterdam), 159–179.Google Scholar
• Bakker W, Catanese G, Koole G, Li S, Roubos A (2019) More precision with less data: A new approach to intra-day patterns. Accessed September 2, 2020, www.ccmath.com/spline-method.Google Scholar
• Bassamboo A, Harrison JM, Zeevi A (2006) Design and control of a large call center: Asymptotic analysis of an LP-based method. Oper. Res. 54(3):419–435.Link, Google Scholar
• Bhulai S, Koole GM (2003) A queueing model for call blending in call centers. IEEE Trans. Automatic Control 48(8):1434–1438.Google Scholar
• Bhulai S, Pot SA, Koole GM (2008) Simple methods for shift scheduling in multi-skill call centers. Manufacturing Service Oper. Management 10(3):411–420.Link, Google Scholar
• Bodur M, Luedtke JR (2017) Mixed-integer rounding enhanced Benders decomposition for multiclass service-system staffing and scheduling with arrival rate uncertainty. Management Sci. 63(7):2073–2091.Link, Google Scholar
• Braverman A (2020) Steady-state analysis of the join-the-shortest-queue model in the Halfin–Whitt regime. Math. Oper. Res. 45(3):1069–1103.Link, Google Scholar
• Bromley L (2001) Erlang for Excel. Accessed September 7, 2020, www.erlang.co.uk.Google Scholar
• Brown L, Gans N, Mandelbaum A, Sakov A, Shen H, Zeltyn S, Zhao L (2005) Statistical analysis of a telephone call center: A queueing-science perspective. J. Amer. Statist. Assoc. 100(469):36–50.Google Scholar
• Cezik MT, L’Ecuyer P (2008) Staffing multiskill call centers via linear programming and simulation. Management Sci. 54(2):310–323.Link, Google Scholar
• Chan W, Koole G, L’Ecuyer P (2014a) Dynamic call center routing policies using call waiting and agent idle times. Manufacturing Service Oper. Management 16(4):544–560.Link, Google Scholar
• Chan W, Ta TA, L’Ecuyer P, Bastin F (2016) Two-stage chance-constrained staffing with agent recourse for multi-skill call centers. 2016 Winter Simulation Conf. (IEEE, Piscataway, NJ), 3189–3200.Google Scholar
• Chan W, Ta TA, L’Ecuyer P, Bastin F, Tolk A, Diallo SY, Ryzhov IO, Yilmaz L, Buckley S (2014b) Chance-constrained staffing with recourse for multi-skill call centers with arrival-rate uncertainty. Proc. 2014 Winter Simulation Conf. (IEEE Press, Piscataway, NJ), 4103–4104.Google Scholar
• Channouf N, L’Ecuyer P (2012) A normal copula model for the arrival process in a call center. Internat. Trans. Oper. Res. 19(6):771–787.Google Scholar
• Chevalier P, Tabordon N (2004) Overflow analysis and cross-trained servers. Internat. J. Production Econom. 85:47–60.Google Scholar
• Chevalier P, Shumsky RA, Tabordon N (2004a) Routing and staffing in large call centers with specialized and fully flexible servers. Google Scholar Accessed September 8, 2020.Google Scholar
• Chevalier P, Shumsky RA, Tabordon N (2004b) Routing and staffing in large call centers with specialized and fully flexible servers. Manufacturing Service Oper. Management. Accessed 14 June 2023, http://mba.tuck.dartmouth.edu/pages/faculty/robert.shumsky/xtrain_large_cc.pdf.Google Scholar
• Cleveland B (2019) Call Center Management on Fast Forward. ICMI, Colorado Springs (CO) (Call Center Press).Google Scholar
• Crow EL (1958) The mean deviation of the Poisson distribution. Biometrika 45(3–4):556–562.Google Scholar
• Cui L, Tezcan T (2016) Approximations for chat service systems using many-server diffusion limits. Math. Oper. Res. 41(3):775–807.Link, Google Scholar
• Dantzig GB (1954) A comment on Edie’s “Traffic delays at toll booths.” J. Oper. Res. Soc. Amer. 2(3):339–341.Link, Google Scholar
• Deslauriers A, L’Ecuyer P, Pichitlamken J, Ingolfsson A, Avramidis AN (2007) Markov chain models of a telephone call center with call blending. Comput. Oper. Res. 34(6):1616–1645.Google Scholar
• Ding S, Koole GM (2022) Optimal call center forecasting and staffing. Probab. Engrg. Informational Sci. 36(2):254–263.Google Scholar
• Ding S, Koole G, van der Mei RD (2015) On the estimation of the true demand in call centers with redials and reconnects. Eur. J. Oper. Res. 246(1):250–262.Google Scholar
• Ding S, Li S, Koole G, Yuce EI, van der Mei R, Stolletz R (2020) Data analysis and validation of call center staffing and workforce models. Working paper, Vrije Universiteit, Amsterdam.Google Scholar
• Dixon M, Toman N, Delisi R (2013) The Effortless Experience (Penguin, New York).Google Scholar
• Feigin P (2006) Analysis of customer patience in a bank call center. Working paper, The Technion, Haifa, Israel.Google Scholar
• Fukunaga A, Hamilton E, Fama J, Andre D, Matan O, Nourbakhsh I (2002) Staff scheduling for inbound call centers and customer contact centers. AI Magazine 23(4):30–40.Google Scholar
• Gamarnik D, Stolyar AL (2012) Multiclass multiserver queueing system in the Halfin–Whitt heavy traffic regime: Asymptotics of the stationary distribution. Queueing Systems 71(1–2):25–51.Google Scholar
• Gans N, Zhou Y-P (2003) A call-routing problem with service-level constraints. Oper. Res. 51(2):255–271.Link, Google Scholar
• Gans N, Zhou Y-P (2007) Call-routing schemes for call-center outsourcing. Manufacturing Service Oper. Management 9(1):33–50.Link, Google Scholar
• Gans N, Koole GM, Mandelbaum A (2003) Telephone call centers: Tutorial, review, and research prospects. Manufacturing Service Oper. Management 5(2):79–141.Link, Google Scholar
• Gans N, Liu N, Mandelbaum A, Shen H, Ye H (2010) Service times in call centers: Agent heterogeneity and learning with some operational consequences. IMS Collections 6:99–123.Google Scholar
• Gans N, Shen H, Zhou Y-P, Korolev N, McCord A, Ristock H (2015) Parametric forecasting and stochastic programming models for call-center workforce scheduling. Manufacturing Service Oper. Management 17(4):571–588.Link, Google Scholar
• Ghareeb ET, Abd Elatif MM, El Bakry HM (2016) Optimal routing selection using analytical hierarchy process. Internat. J. Adv. Comput. Techn. 8(3):44–57.Google Scholar
• Global Industry Analysts, Inc. (2023) Call Centers: Global Strategic Business Report. Accessed June 14, 2023, https://www.researchandmarkets.com/reports/338444/call_centers_global_strategic_business_report.Google Scholar
• Green L, Kolesar P (1991) The pointwise stationary approximation for queues with nonstationary arrivals. Management Sci. 37(1):84–97.Link, Google Scholar
• Gurvich I, Perry O (2012) Overflow networks: Approximations and implications to call center outsourcing. Oper. Res. 60(4):996–1009.Link, Google Scholar
• Gurvich I, Luedtke J, Tezcan T (2010) Staffing call centers with uncertain demand forecasts: A chance-constrained optimization approach. Management Sci. 56(7):1093–1115.Link, Google Scholar
• Halfin S, Whitt W (1981) Heavy-traffic limits for queues with many exponential servers. Oper. Res. 29(3):567–587.Link, Google Scholar
• Harrison JM, Zeevi A (2004) Dynamic scheduling of a multiclass queue in the halfin-whitt heavy traffic regime. Oper. Res. 52(2):243–257.Link, Google Scholar
• Harrison JM, Zeevi A (2005) A method for staffing large call centers based on stochastic fluid models. Manufacturing Service Oper. Management 7(1):20–36.Link, Google Scholar
• Hasija S, Pinker EJ, Shumsky RA (2008) Call center outsourcing contracts under information asymmetry. Management Sci. 54(4):793–807.Link, Google Scholar
• Hathaway BA, Emadi SM, Deshpande V (2017) Queue now or queue later: An empirical study of callers’ redial behaviors. Working paper. Accessed June 14, 2023, https://kenaninstitute.unc.edu/publication/queue-now-or-queue-later-an-empirical-study-of-callers-redial-behaviors/.Google Scholar
• Hathaway BA, Emadi SM, Deshpande V (2020) Don’t call us, we’ll call you: An empirical study of caller behavior under a callback option. Management Sci. 67(3):1508–1526.Google Scholar
• Huang H, Jiang M, Ding Z, Zhou M (2019) Forecasting emergency calls with a Poisson neural network-based assemble model. IEEE Access 7:18061–18069.Google Scholar
• Hyndman RJ (2013) Forecasting with daily data. Accessed June 26, 2020, robjhyndman.com/hyndsight/dailydata.Google Scholar
• Hyndman RJ, Athanasopoulos G (2018) Forecasting: Principles and Practice (O Texts).Google Scholar
• Ibrahim R, L’Ecuyer P (2013) Forecasting call center arrivals: Fixed-effects, mixed-effects, and bivariate models. Manufacturing Service Oper. Management 15(1):72–85.Link, Google Scholar
• Ibrahim R, Whitt W (2009) Real-time delay estimation based on delay history. Manufacturing Service Oper. Management 11(3):397–415.Link, Google Scholar
• Ibrahim R, Whitt W (2011) Wait-time predictors for customer service systems with time-varying demand and capacity. Oper. Res. 59(5):1106–1118.Link, Google Scholar
• Ibrahim R, L’Ecuyer P, Shen H, Thiongane M (2016a) Inter-dependent, heterogeneous, and time-varying service-time distributions in call centers. Eur. J. Oper. Res. 250(2):480–492.Google Scholar
• Ibrahim R, Ye H, L’Ecuyer P, Shen H (2016b) Modeling and forecasting call center arrivals: A literature survey and a case study. Internat. J. Forecasting 32(3):865–874.Google Scholar
• Jack EP, Bedics TA, McCary C (2006) Operational challenges in the call center industry: A case study and resource based framework. Management Service Quality 16(5):477–500.Google Scholar
• Jalal ME, Hosseini M, Karlsson S (2016) Forecasting incoming call volumes in call centers with recurrent neural networks. J. Bus. Res. 69(11):4811–4814.Google Scholar
• Jongbloed G, Koole GM (2001) Managing uncertainty in call centers using Poisson mixtures. Appl. Stochastic Models Bus. Indust. 17(4):307–318.Google Scholar
• Jouini O, Akşin Z, Dallery Y (2011) Call centers with delay information: Models and insights. Manufacturing Service Oper. Management 13(4):534–548.Link, Google Scholar
• Jouini O, Dallery Y, Rabie N-A (2008) Analysis of the impact of team-based organizations in call center management. Management Sci. 54(2):400–414.Link, Google Scholar
• Jouini O, Koole GM, Roubos A (2013) Performance indicators for call centers with impatience. IIE Trans. 45(3):341–354.Google Scholar
• Kaplan EL, Meier P (1958) Nonparametric estimation from incomplete observations. J. Amer. Statist. Assoc. 53(282):457–481.Google Scholar
• Kim S, Whitt W (2014) Are call center and hospital arrivals well modeled by nonhomogeneous Poisson processes? Manufacturing Service Oper. Management 16(3):464–480.Link, Google Scholar
• Koole GM (2013) Call Center Optimization (MG books, Amsterdam).Google Scholar
• Koole GM, van der Sluis HJ (2003) Optimal shift scheduling with a global service level constraint. IIE Trans. 35(11):1049–1055.Google Scholar
• Legros B (2017) Reservation, a tool to reduce the balking effect and the probability of delay. Oper. Res. Lett. 45(6):592–597.Google Scholar
• Legros B, Jouini O (2019) On the scheduling of operations in a chat contact center. Eur. J. Oper. Res. 274(1):303–316.Google Scholar
• Legros B, Jouini O, Dallery Y (2015a) A flexible architecture for call centers with skill-based routing. Internat. J. Production Econom. 159:192–207.Google Scholar
• Legros B, Jouini O, Koole G (2016) Optimal scheduling in call centers with a callback option. Performance Evaluation 95:1–40.Google Scholar
• Legros B, Jouini O, Koole GM (2015b) Adaptive threshold policies for multi-channel call centers. IIE Trans. 47(4):414–430.Google Scholar
• Legros B, Ding S, van der Mei R, Jouini O (2017) Call centers with a postponed callback offer. OR Spectrum 39(4):1097–1125.Google Scholar
• Li S, Koole G (2020) An adaptive call center routing policy. Working paper.Google Scholar
• Li S, Koole G, Jouini O (2019) A simple solution for optimizing weekly agent scheduling in a multi-skill multi-channel contact center. Proc. 2019 Winter Simulation Conf. (IEEE, Piscataway, NJ), 3657–3668.Google Scholar
• Li S, Wang Q, Koole G (2020a) Optimal contact center staffing and scheduling with machine learning. Working paper.Google Scholar
• Li S, Koole G, Yuce EI, Catanese G (2020b) A machine learning approach to call center staffing. Working paper.Google Scholar
• Liao S, van Delft C, Vial J-P (2013) Distributionally robust workforce scheduling in call centres with uncertain arrival rates. Optim. Methods Software 28(3):501–522.Google Scholar
• Liao S, Koole G, van Delft C, Jouini O (2012) Staffing a call center with uncertain non-stationary arrival rate and flexibility. OR Spectrum 34(3):691–721.Google Scholar
• Luo J, Zhang J (2013) Staffing and control of instant messaging contact centers. Oper. Res. 61(2):328–343.Link, Google Scholar
• Maister DH (1985) The psychology of waiting lines. Czepiel J, Solomon MR, Surprenant CF, eds. The Service Encounter (Lexington Books).Google Scholar
• Makridakis SG (1990) Forecasting, Planning, and Strategies for the 21st Century (The Free Press).Google Scholar
• Mandelbaum A, Stolyar AL (2004) Scheduling flexible servers with convex delay costs: Heavy-traffic optimality of the generalized cμ-rule. Oper. Res. 52(6):836–855.Link, Google Scholar
• Mandelbaum A, Zeltyn S (2004) The impact of customers’ patience on delay and abandonment: Some empirically-driven experiments with the m/m/n + g queue. OR Spectrum 26(3):377–411.Google Scholar
• Mattia S, Rossi F, Servilio M, Smriglio S (2017) Staffing and scheduling flexible call centers by two-stage robust optimization. Omega 72:25–37.Google Scholar
• Mazareanu E (2019) Call center market size by region 2012-2017. Accessed June 22, 2020, www.statista.com/statistics/881033/call-center-market-size-region.Google Scholar
• Mehrotra V, Ross K, Ryder G, Zhou Y-P (2012) Routing to manage resolution and waiting time in call centers with heterogeneous servers. Manufacturing Service Oper. Management 14(1):66–81.Link, Google Scholar
• Milner JM, Olsen TL (2008) Service-level agreements in call centers: Perils and prescriptions. Management Sci. 54(2):238–252.Link, Google Scholar
• Palm C (1953) Methods of judging the annoyance caused by congestion. Tele 4:189–208.Google Scholar
• Pang G, Perry O (2015) A logarithmic safety staffing rule for contact centers with call blending. Management Sci. 61(1):73–91.Link, Google Scholar
• Pot SA, Bhulai S, Koole GM (2008) A simple staffing method for multi-skill call centers. Manufacturing Service Oper. Management 10(3):421–428.Link, Google Scholar
• Powell SG, Baker KR, Lawson B (2009) Impact of errors in operational spreadsheets. Decision Support Systems 47(2):126–132.Google Scholar
• Price B, Jaffe D (2008) The Best Service Is No Service (Wiley).Google Scholar
• Reed J (2009) The g/gi/n queue in the Halfin–Whitt regime. Ann. Appl. Probab. 19(6):2211–2269.Google Scholar
• Robbins TR, Harrison TP (2010) A stochastic programming model for scheduling call centers with global service level agreements. Eur. J. Oper. Res. 207(3):1608–1619.Google Scholar
• Roubos A, Jouini O (2013) Call centers with hyperexponential patience modeling. Internat. J. Production Econom. 141(1):307–315.Google Scholar
• Roubos A, Bhulai S, Koole GM (2017) Flexible staffing for call centers with non-stationary arrival rates. Boucherie RJ, van Dijk NM, eds. Markov Decision Processes in Practice (Springer), 487–503.Google Scholar
• Roubos A, Koole G, Stolletz R (2012) Service-level variability of inbound call centers. Manufacturing Service Oper. Management 14(3):402–413.Abstract, Google Scholar
• Saltzman RM, Mehrotra V (2001) A call center uses simulation to drive strategic change. Interfaces 31(3):87–101.Link, Google Scholar
• Shen H, Huang J (2008) Interday forecasting and intraday updating of call center arrivals. Manufacturing Service Oper. Management 10(3):391–410.Link, Google Scholar
• Soyer R, Tarimcilar MM (2008) Modeling and analysis of call center arrival data: A Bayesian approach. Management Sci. 54(2):266–278.Link, Google Scholar
• Steckley SG, Henderson SG, Mehrotra V (2004) Service system planning in the presence of a random arrival rate. Technical report, Cornell University Operations Research and Industrial Engineering.Google Scholar
• Stolletz R (2008) Approximation of the non-stationary m(t)/m(t)/c(t)-queue: The stationary backlog-carryover approach. Eur. J. Oper. Res. 190(2):478–493.Google Scholar
• Sze DY (1984) A queueing model for telephone operator staffing. Oper. Res. 32(2):229–249.Link, Google Scholar
• Tan TF, Netessine S (2014) When does the devil make work? An empirical study of the impact of workload on worker productivity. Management Sci. 60(6):1574–1593.Link, Google Scholar
• Taylor JW (2008) A comparison of univariate time series methods for forecasting intraday arrivals at a call center. Management Sci. 54(2):253–265.Link, Google Scholar
• Tezcan T, Zhang J (2014) Routing and staffing in customer service chat systems with impatient customers. Oper. Res. 62(4):943–956.Link, Google Scholar
• TrustRadius (2020) Call center workforce optimization software. Accessed September 8, 2020, www.trustradius.com/call-center-workforce-optimization.Google Scholar
• van Eeden K, van der Hilst E, Koole G (2013) Errors in the Erlang97 Excel add-in module. Accessed September 7, 2020, www.gerkoole.com/publications.Google Scholar
• Wallace RB, Whitt W (2005) A staffing algorithm for call centers with skill-based routing. Manufacturing Service Oper. Management 7(4):276–294.Link, Google Scholar
• Ward AR, Armony M (2013) Blind fair routing in large-scale service systems with heterogeneous customers and servers. Oper. Res. 61(1):228–243.Link, Google Scholar
• Weinberg J, Brown LD, Stroud JR (2007) Bayesian forecasting of an inhomogeneous poisson process with applications to call center data. J. Amer. Statist. Assoc. 102(480):1185–1198.Google Scholar
• Whitt W (2005) Engineering solution of a basic call-center model. Management Sci. 51(2):221–235.Link, Google Scholar
• Whitt W (2006) Staffing a call center with uncertain arrival rate and absenteeism. Production Oper. Management 15(1):88–102.Google Scholar
• Ye H, Brown LD, Shen H (2020) Hazard rate estimation for call center customer patience time. IISE Trans. 52(8):890–903.Google Scholar
• Zeltyn S, Mandelbaum A (2005) Call centers with impatient customers: Many-server asymptotics of the M/M/n+G queue. Queueing Systems 51:361–402.Google Scholar
• Zhan D, Ward AR (2014) Threshold routing to trade off waiting and call resolution in call centers. Manufacturing Service Oper. Management 16(2):220–237.Link, Google Scholar