Don’t Kill Telephony: Why Good ASR and ACD Scores Matter


6 min reading time

Scary robot with four arms ending in telephones

A quick FAQ about ASR and ACD scores, how to keep them healthy and why this is important for the telecom industry

How do I calculate ASR and ACD?

If you have experience with call centers, you’ve surely heard of ASR (average-seizure ratio) and ACD (average call duration).  Just in case you need a quick refresher, ASR is the percentage of calls that are successfully connected relative to the number of attempted calls:

ASR % = (total number of answered calls / total number of calls) × 100

As its name suggests, ACD is the average length of calls made over a given network.  

ACD = duration of all answered calls / number of answered calls

Sometimes, carriers also refer to ACD as ‘ALOC’ – Average Length of Call.

Both metrics are used to assess network quality.  It’s especially important for call centers to be aware of these scores and keep them within a “reasonable” range, for reasons explained below.

What’s a “good” ASR and ACD for a call center?

ASR and ACD scores which are too low indicate a poor quality of traffic passing through networks’ infrastructures.

An exceptionally good ASR score for a call center would be 60% or above. 40% – 50% is considered acceptable.  Anything below 40% is considered quite poor.

For ACD, calls lasting longer than 6 minutes are excellent, while anything at the 3 or 4 minute mark is considered acceptable.  Anything below 1 minute should be considered very problematic.

Does this vary according to country or industry?

Yes, ASR or ACD scores can vary by geographic location, principally due to the quality of the network in that area. Industry and brand matter as well: if you’re selling a complex product or one with good brand recognition, ACD can be relatively high. However, certain calls are perceived as less desirable than others: for tax optimization calls (frequent in France), as well as sales calls for phone or internet subscriptions, ACD can dip quite low, and pick up rates might even be non-existent.

What does it mean if I have a low ASR / ACD score?

In a call center context, low ASR or ACD scores can be caused by a variety of factors:


User behavior: For a call center, low ASR rates can indicate that large volumes of calls, sometimes with the help of dialers, are being attempted with nobody picking up.  Low pick up rates may be because callee lists are out of date (bad numbers), callees recognize traffic as “undesirable” and do not pick up, or callees are not available to pick up (calls to home phones during normal working hours). Individuals who feel harassed by unsolicited phone calls may in turn express dissatisfaction with the network operator.

Predictive dialer set up not optimized: Though call centers may be tempted to use dialers at their highest volume to spike productivity in the short term, this will have consequences on the ASR in the long run and ultimately, due to carrier limits, make the center less effective.

Call centers should aim to hit the “sweet spot” of productivity: if dialers don’t dial fast enough, agents will be idle and productivity will drop.  However, if dialing speeds are too aggressive, many calls will end up cancelled since all agents will be occupied, which in turn leads to very low ASR. Indeed, aggressive predictive dialing speeds is one of the common causes of call centers’ having low ASR. Try and find a rhythm which hits a balance between idle agents and cancelled calls.

Busy signals from call recipient: if a call is attempted and reaches a busy destination line, this will count as a failed call.

Far-end switch congestion: This indicates that a call center is making too many calls to the same geographic location (building, small town) for the local switch board to handle.


Similarly, low ACD (below 3 minutes) can indicate that the call recipient isn’t interested in the caller’s purpose, and doesn’t see any value in a discussion.

However, other factors may also be at fault:

Audio quality: Audio problems, like voices sounding distant, echoing or cutting out (caused by low quality codecs, jitter or packet loss), as well as “dead air,” may cause a call recipient to terminate the call quickly. NAT problems (having to do with poor internet configurations), often cause a ‘one way audio’ effect, which leads to hang ups.

Call centers also need to make sure they don’t oversaturate their internet connection. For example, with ADSL, there will always be a limit of agents you can set up while maintaining good audio quality. Again, surpassing this limit will decrease your audio quality.

Looping: Repeatedly redialing a wrong phone number will make ASR scores drop.

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Why do these metrics matter?

Network operators dislike low ASR / ACD scores because they reflect negatively on their quality.  Furthermore, calls which are not picked up or which do not last very long do not generate much revenue for networks, but still take up their resources.  This can cause friction between network operators and customer call centers. Carriers may end up blocking those whose scores are too poor, or else increasing their prices or switching them to “dedicated” channels for low quality traffic. Keeping scores within a reasonable range can help maintain good working relationships between the two.

On a more macroscopic scale, marketing, polling and outbound sales initiatives via telephone will only remain effective if the people called can be reached, and messages transmitted.  In other words, if call quality decreases too much or people feel “spammed”, individuals will be more and more inclined to subscribe to do not call lists, complain to government regulators, not pick up to unknown numbers or even screen calls by letting them go to voicemail.

Keeping the “telephone experience” reasonably pleasant for consumers will mean that it stays a potent channel for communication – degrading its quality beyond a certain point will ultimately kill any efficacy it has as a marketing, sales or survey tool.

How can I fix a low ASR / ACD?

  1. Before a campaign: You can run a HLR (Home Location Register) check to verify which mobile phone numbers are invalid before even making any calls.  After a call campaign: Clean your database by removing non-attributed numbers by checking your CDRs (Call Detail Record).
  1. Tune your predictive dialing software to hit the productivity “sweet spot”: attain the perfect balance between always having an agent on the phone without having prospects pick up to “dead air.” Check this with your software vendor.
  1. Optimize how you target your audience: call at times that are convenient for them, segment your call list for people who are truly susceptible to be interested in your offer. Call campaigns which bother too many of your consumers will make your ASR and ACD scores suffer accordingly.