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How to increase call center staffing with Erlang C calculator

Expert Lori Bocklund explains the best way call center management can calculate call volume and help with the need to increase call center staffing with Erlang C.

I supervise a call center of seven agents for a credit union. We are in the midst of an upgrade to our core processor...

and are being told to expect an increase in call volumes by 300 percent for the first couple of weeks after we go live. I've created a staffing model using an online Erlang C calculator. However, management is not familiar with this formula and does not think it is accurate. They are suggesting that I use "hours of work that need to be supported in a 30-minute increment." I'm not familiar with this formula. I used what was provided and its results are double what Erlang C provided. For example, our highest volume hour (at 300 percent increase) is 257 calls. Erlang C calculated a need for 17 agents. However, the "hours of work" formula states I need 34 agents. Can you provide any feedback on either of the formulas? Or perhaps suggest a better solution for a small call center that temporarily needs to increase call center staffing.

Erlang is important to use in call center staffing because it factors in “random call arrival” patterns, whereas straight workload calculations are linear and do not. You should use Erlang C calculations, along with appropriate considerations of shrinkage. We also advocate educating call center management on the concepts of the Erlang formula, which is easy to do using a calculator. Show them some examples using the calculator with different volumes (e.g., your current peak hour volume and the 300 percent increase). And if they want to understand more about the concepts, buy them a copy of the book “Call Center Management of Fast Forward” by Brad Cleveland (available on Amazon or from ICMI).

A 300 percent volume increase should not drive a nearly 500 percent staff increase (from your current seven agents to the projected 35 agents using the “hours of work” formula your management is suggesting). In fact, because call centers that handle a greater volume and have more staff are inherently more efficient, you should be able to handle the 300 percent volume increase with less than a 300 percent increase in staff, which is what your Erlang models are showing you (increasing to 17 agents from seven being about a 242 percent increase).

You haven’t mentioned any impact on your handle time due to the system change. If you expect handle time to go up as well, make sure your calculations take that into account.

It is important to remember when you are using a calculator that the calculator is totally dependent upon accurate information. If your calculator allows you to input shrinkage factors (absenteeism, breaks and lunches, etc.) make sure they are as accurate as possible. If it does not allow you to do that, then make sure you add it to your end requirement. Example: If the calculator says you need 10 people with no shrinkage factor and your total staff shrinkage factor is 25 percent, then you need to add 2.5 full-time employees (10*1.25=12.5) with shrinkage.

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