Modeling the IRS Telephone Taxpayer Information System

Abstract

The Internal Revenue Service (IRS) toll-free, nationwide telephone system provides prompt tax-information assistance. In 1986, the IRS processed 37.8 million calls from taxpayers at 32 answering sites. This paper documents a critical review of the IRS approach to allocating its staff and equipment. We built a simulation-based model to test various allocation policies for deploying IRS resources. The simulation study included detailed sensitivity analysis on key network variables, and showed the feasibility of modeling a typical IRS location as a multiserver loss/delay queue with retrial and reneging. The second phase of this effort therefore centered around developing a prototype probabilistic model for determining the most effective way of providing service at reasonable levels and at minimum cost. The resulting model allows the IRS to determine from tables the best configuration of people and telephone lines for any expected levels of incoming traffic. In addition, we provided flow balance analyses of the underlying feedback queues that permit the IRS to separate their caller streams into fresh and repeat callers, and thus to estimate actual demand for service.

Statistical Analysis of a Telephone Call Center

“…It does not acknowledge, among other things, customer abandonment behavior, time-dependent parameters, or customer heterogeneity. We refer the reader to Sze (1984), Harris, Hoffman and Saunders (1987), Garnett and Mandelbaum (1999), Garnett et al (2002) and Zohar et al (2002) for an elaboration of the Erlang-C's shortcomings. An essential task of queueing theorists is to develop models that account for the most important of these effects.…”

Telephone Call Centers: Tutorial, Review, and Research Prospects

“…One example is Kort (1983), which summarizes models of the Bell System Public Switched Telephone Network, developed in the 70s and 80s. Another is Harris et al (1987), which analyzes IRS call centers. Our experience has frequently confirmed these findings for human services that are homogeneous and unpaced (not only telephone services).…”

Designing a Call Center with Impatient Customers

“…In Harris et al (1987) and Hoffman and Harris (1986) the basic model is M/M/N, with the addition of abandonment, retrials, and a variety of service disciplines. Assuming a heavily-loaded call center and using some approximations, they arrive at a system of steady-state equations that can be solved numerically.…”