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WFM Glossary

Workforce Management Terminologies, definitions, formulas and Erlang calculators!

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Browse the glossary using this index

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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.


A forecasting term meaning that a pattern repeats itself, in call centers typically at intra-day, intra-week and intra-year level.

Short Abandon

A call that abandoned very quickly making it unlikely that the caller was already tired of waiting.


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 to evaluate the performance of such a system.

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, a somewhat ambiguous term that in the broad sense can refer to all aspects of service (waiting time, abandonments, and so forth). In the narrow sense, it is defined as the percentage of calls answered within the AWT. The industry standard is 80/20: 80% of the calls have to be answered within 20 seconds. Quality of Service is a synonym of the former broader 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.