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WFM Glossary

WFM cycleWorkforce Management definitions and formulas

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Safety Staffing

The additional number of agents needed to reach a certain service level. The safety staffing level is often calculated by means of the Erlang-C or Erlang-X formulas.


Skill(s)-based routing, the fact that different types of calls are routed to different agent groups based on the type of the call and the skills of the agents.


The process of deciding how to commit resources between a variety of possible tasks.

Short Abandon

A call that is abandoned by the calling party before a connection with an agent is made with 2 conditions:

1. The call is queued 

2. The call is abandoned within a predetermined short abandonment threshold

The reason that short abandons are mentioned separately from regular abandoned calls is short abandons should not be included in service level calculations. The reason behind this line of thinking is that a customer that hangs up within the the short abandonment threshold does not give the contact center agent enough time to pick up the phone. 


The fraction of paid time that an agent is not available for taking calls because of holidays, training, paid breaks, etc.

Below you can see an example of a shrinkage table. It is important to note that this is merely an example to illustrate how shrinkage is calculated. There can be many more activities that can be added and not all activities are relevant for all companies.


The activity of mimicking a real-world system over time, usually performed with a computer. The goal of simulation is to quickly evaluate the performance of such a system, and see how the system behaves by changing some variables. Simulation is also often used to approximate solutions to problems when there is no numerical solution

Skill Group

A group of agents all having the same skill set.

Skill Set

The set of skills that an agent or group of agents have.


Service Level, an somewhat ambiguous term that can relate to all aspects of service (waiting time, abandonments, and so forth). In call centers usually defined as the percentage of calls answered within the AWT. Quality of Service is a synonym of the former meaning.


Service Level Agreement, the contract between a business unit and higher management or an outsourcer with its client company concerning the required service levels.


An agent who can only handle one type of call. It can also mean an agent who can do even the most difficult calls, in contrast with a generalist. To avoid ambiguity it is better to use the term single-skilled agent.


Single skill first, an agent selection rule used in multi-skill call centers, that assigns calls to agents with the least number of skills.


Service Time, see AWT.