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Glossary · Call centre operations

What is Service level?

  • Also called: sla, 80/20 rule

Reviewed by Sujan ThapaliyaLast updated

Definition

Service level is the percentage of inbound calls answered within a target time, conventionally written as 80/20: 80% of calls answered within 20 seconds. It is the standard measure of whether a queue is adequately staffed.
The three STIR/SHAKEN attestation levels, which underpin how service level behaves in practice: A asserts both that the carrier knows the customer and that the customer may use the calling number, B asserts the customer only, and C asserts neither. A shared number pool can reach B at best, which is why number ownership keeps recurring in these definitions.
Attestation is the backdrop to most caller-ID and deliverability terms, service level included.

In practice

How service level actually works

80/20 is a convention, not a law of nature. The right target depends on what the caller is calling about; an emergency line and a billing enquiry line should not share one.

Abandonment is the honest companion metric. A queue can hit its service level while abandoning heavily if the calls that waited longest hung up before being counted.

Service level is also the metric most sensitive to how the queue is configured rather than how it is staffed. Changing the overflow rule, the callback threshold or the point at which a caller enters the queue all move the number without a single extra agent, which is why it should be read next to abandonment rather than alone.

Both numbers are yours to set. Copying 80/20 without checking your callers is how a target becomes decoration.
TargetReads asSuits
80/2080% answered within 20 secondsThe conventional default, not a standard
90/1590% within 15 secondsPremium support, priced accordingly
70/6070% within 60 secondsLow-urgency queues where callers tolerate waiting
Daily averageNothing usefulHides the interval where the queue broke

Worked example

400 calls offered in an interval, 320 answered within 20 seconds, gives 80%. Twelve of the remaining eighty abandoned — which is the number the service level does not show you.

Service level: common questions

What does 80/20 service level mean?
Eighty per cent of calls answered within twenty seconds. It is a convention rather than a standard — the two numbers are yours to set, and copying 80/20 without checking what your callers tolerate is how a target ends up meaningless.
Should service level be measured daily or per interval?
Per interval, usually every half hour. A daily figure hides the hour where a quarter of your callers gave up, and that hour is the only part of the day you could have acted on.
How does service level relate to abandonment?
They move together but measure different things. Service level asks how fast you answered; abandonment asks how many stopped waiting. A queue can hit its service level and still abandon badly if the tail of the distribution is long.

Sources

  1. Combating Spoofed Robocalls with Caller ID Authentication — Federal Communications CommissionThe STIR/SHAKEN framework, the attestation levels carriers sign calls with, and the mandate requiring providers to authenticate caller ID.
  2. 47 U.S.C. § 227 — Restrictions on the use of telephone equipment — Cornell Legal Information InstituteThe Telephone Consumer Protection Act itself — the consent requirements, calling-hours limits, and private right of action.
  3. ITU-T Recommendation E.164 — The international public telecommunication numbering plan — International Telecommunication UnionThe international number format, the 15-digit maximum, and how country codes and national numbers compose.

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