Forecasting Call Volume

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Forecasting Call Volume
Hi There, I have been working in the contact centre industry for the last 20 years, using multiple wfm systems and Erlang calculators to determine staffing requirements at interval level as well as wte capacity planning.

I have always used offered calls in the modelling calculations and they have always worked really well but recently I've been challenged on this, suggesting that it should be answered calls. My nervousness with working out staffing requirements using answered calls means I would be planning on a lower number, resulting in lower wte requirement and increasing likelyhood of abandoning more calls.
I've read through some of the forums however some of the answers go back to 2005 (Dave Appleby) at the time agrees with the offered rationale but just looking for some reassurance

Thanks
K

Helper

Call Centre Helper

Offered calls is right
Hi Karen

Offered calls is the right approach as otherwise you will always be under staffed. If you just look at answered calls you be ignoring service levels and if you will tend to be understaffed and then abandons will go up.

There is a problem though that most Erlang calculators (based on the Erlang C model) assume that people have unlimited patience. This can result in them giving a rather pessimistic approach. Mr Erlang himself talked about this.

The alternative approach is to look at the Erlang A model (A stands for Abandons) which does model this behaviour, and a lot of the academic research seems to point may be more accurate. This was developed in the late 1940s by Conny Palm.

There is a paper here
http://iew3.technion.ac.il/serveng/References/Erlang_A_Avi.pdf

I have been looking at the Erlang A formula and have built a prototype calculator, but it is not yet suitable for release. If you wanted to send me some of your figures I would be happy to run them and compare results.

Thanks

Jonty

Thanks Jonty
Thanks for your quick response. That's really helpful. :-)

Continued
I would welcome the opportunity to send some raw numbers data to compare results Jonty. I'm back at work next week. Kind Regards, Karen

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