the math of contact center staffingswpp.org/wp-content/uploads/2016... · inbound call center...

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The Math of Contact Center Staffing

2016 Annual Conference

© Copyright Reynolds/Klenke 2015

Session Overview

In this session, you will learn to:  Outline the implications of overstaffing and understaffing.   Identify the unique characteristics and requirements for

inbound call center staffing.   Identify staffing models for inbound call centers.  Calculate staff requirements to meet service goals.   Identify basic call center staffing tradeoffs.   Identify small versus large group size considerations.  Outline steps for staffing for outbound calls, emails, and

chat contacts.


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Call Center Staffing

Call center success depends on getting the

right number of people for each period of the day

to answer incoming contacts at a desirable level of service while

minimizing cost


Implications of Getting it Wrong

Overstaffing

Understaffing

When considering the impact of adding or subtracting staff, consider the impact on three main stakeholder groups:

Customers Frontline Staff Management


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Impact on The Customer

Overstaffing

 Faster service

 Expectation of future service

Understaffing

 Long delays

 Reduced quality of service

 Abandoned calls


Service Implications

Think about the wait in queue from the customer’s perspective.


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Queue Perspectives

In-Person Queue

 See the queue

 Select a queue

 Watch progress

 Estimate time


Queue Perspectives

Telephone Queue

  Invisible queue

 Limited choices

 No sign of progress

 No idea of time


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Impact on Frontline Staff

Overstaffing

 More idle time

 Less productive

 Boredom

Understaffing

 Less idle time

 More stress

 Angry callers


Impact on Management

Overstaffing

 Excessive costs

 Lower productivity

Understaffing

 Unhappy callers

 Unhappy staff

 Higher phone costs

 Abandoned calls


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Calculating Contact Center Workload

Workload = Call Volume x Average Handle Time (AHT) (expressed in hours of work in a one-hour period)

For AHT in minutes, divide by 60 / For AHT in seconds, divide by 3600

Example: 400 calls per hour, AHT = 180 seconds 400 x 180 / 3600 = 20 hours or erlangs


Workload Arrivals

20 Hours Sequential Versus Random Workload

How many staff?


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Workload Arrivals

20 Hours Sequential Versus Random Workload

20 staff > 20 staff


Defining Speed of Answer Goals

 Service level x% of calls answered in y seconds  Average speed of answer (ASA) (Average delay of all calls – including calls with no wait)


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 What is your service goal?

 When did you set the goal?

 How do you measure success?

 How do you compare to others?

A Discussion About Setting Service Goals


A View of Service Level

Time of Day Call Volume Daily % SL (in 20 sec)

6:00 – 7:00 85 4.5% 100%

7:00 – 8:00 90 5.0% 95%

8:00 – 9:00 95 5.5% 95%

9:00 – 10:00 145 8.0% 90%

10:00 – 11:00 185 10.0% 75%

11:00 – 12:00 195 10.5% 70%

12:00 – 1:00 165 9.0% 80%

1:00 – 2:00 185 10.0% 80%

2:00 – 3:00 220 12.0% 65%

3:00 – 4:00 210 11.0% 70%

4:00 – 5:00 145 8.0% 80%

5:00 – 6:00 125 6.5% 85%

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Staffing for Service Goal with Erlang C

1. Calculate staff workload. Call volume: 400 calls Talk time: 150 sec Wrap-up time: 30 sec AHT: 180 sec Workload = 400 x 180 / 3600 sec/hour = 20 hours

2. Define service goal. Desired speed of answer = ASA <30 seconds

3. Determine staff to meet service objective.


 Need model to predict what will happen in simple incoming call situation with:

  Erlangs of workload

  Varying staffing levels

 Erlang C assumptions – Random call arrivals – Infinite queue

 Other traffic models – Erlang-Engset (smooth workload) – Equivalent Random Theory (peaked traffic)

Staffing Calculations


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Erlang C will fit most simple call center staffing scenarios

Erlang C Formula:

Staffing Calculations

where:"A is the total traffic offered in units of erlangs!N is the number of servers!PW is the probability that a customer has to wait for service


Staffing with Erlang C

Workload Hours

Number of Staff

ASA Service Level (30 sec)

Staff Occupancy

20 21 137 sec 35% .95 20 22 51 sec 59% .91 20 23 25 sec 75% .87 20 24 13 sec 85% .83 20 25 7 sec 91% .80 20 26 4 sec 94% .77


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Evaluate staffing decisions with these tradeoffs in mind:

•  Customer Impact

What is delay time with +/- one agent?

•  Frontline Impact

What is occupancy rate with +/- one agent?

•  Management Impact

What are the financial implications?

Staffing Tradeoffs


Service Tradeoffs

Workload Hours

Number of Staff


Staff Occupancy


What is the impact on service when staff are added or subtracted?


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Productivity Tradeoffs

Workload Hours

Number of Staff


Staff Occupancy


What is the impact on occupancy when staff are added or subtracted?


Financial Tradeoffs

Workload Hours

Number of Staff

ASA Staff Occupancy

20 21 137 sec .95 20 22 51 sec .91 20 23 25 sec .87 20 24 13 sec .83 20 25 7 sec .80 20 26 4 sec .77

86 seconds

What is the impact on revenues and costs when staff are added or subtracted?


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Telephone Costs

1.  Determine additional queue time with missing staff. ASA of 137 versus 51 seconds = 86 seconds per call

2.  Multiply by number of calls. 400 calls x 86 seconds per call = 34,400 seconds

3.  Calculate number of minutes. 34,400 / 60 = 573 minutes of additional queue time

4.  Apply average cost per minute of telephone service. 573 minutes @ 3¢ per minute = $ 17.19 per hour


Impact of Size

Calls /Hour

Staff Workload

Number of Staff

Occupancy Level

Service Level

400 20 hours 23 87% 75% 400 20 hours 24 83% 85% 400 20 hours 25 80% 91%




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Staffing for Other Contacts

Communications with customers occurs over many channels:

  Inbound phone calls   Outbound phone calls   Email   Chat


Calculating Contact Center Workload

Workload = Contact Volume x Average Handle Time (AHT) (expressed in hours of work in a one-hour period)

Incoming Call Example: 400 calls per hour, AHT = 180 seconds 400 x 180 / 3600 = 20 hours or erlangs

Workload calculations be different for:  Outbound calls  Email  Chat


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Calculating AHT for Outbound Calls

In addition to talk time and after-call work, consider front-end set-up time for outbound calls.

Components of Set-Up Time:  Looking up number  Dialing  Waiting for network connect  Waiting for customer connect  Time on non-connects


Call Volume Type of Call Set-up Time Talk Time

40 Answered call

32 sec 135 sec

40 Voice mail

34 sec 0 sec

15 Busy signal

22 sec 0 sec

5 No Answer

46 sec 0 sec

100 calls All Calls 3200 sec 5400 sec

Calculating Set-Up Time


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In this example, 37% of staff time has been spent in just placing the calls. Don’t forget to include this in handle time calculations.

Manual Dialing Results:

3200 seconds set-up

5400 seconds talk time

8600 seconds total time

Call Set-up Time


Calculating Workload for Other Contacts

Considerations for Email Handle Time:

  Is history available?  When does email begin and end?

Considerations for Chat Handle Time:

  Is history available?  How many simultaneous chats?


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Selecting a Staffing Model


Contact Type Work Pattern Model

Outbound calls Sequential Ratio

Email Sequential Ratio

Chat Random Erlang C (modified)

Session Review

In this session, you learned to:  Outline the implications of overstaffing and understaffing.   Identify the unique characteristics and requirements for

inbound call center staffing.   Identify staffing models for inbound call centers.  Calculate staff requirements to meet service goals.   Identify basic call center staffing tradeoffs.   Identify small versus large group size considerations.  Outline steps for staffing for outbound calls, emails, and

chat contacts.


the math of contact center staffingswpp.org/wp-content/uploads/2016... · inbound call center...

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