ASR, ACD and PDD: What They Actually Tell You

When outbound performance drops, the first question is almost always the wrong one. Teams reach for connect rate, see it fall, and start changing things — pacing, list order, agent scripts — without first establishing which layer of the stack moved.

Three carrier-side metrics narrow that down quickly.

ASR — Answer Seizure Ratio

ASR is the ratio of answered calls to total call attempts, expressed as a percentage. It is a carrier-level view of whether your calls are being completed at all.

A useful way to think about it: ASR measures the health of the path between your platform and the person. It is sensitive to:

• List quality. Disconnected, invalid and stale numbers depress ASR without anything being wrong technically.
• Number reputation. If your outbound ANIs are flagged or labeled by analytics providers, carrier and handset-level treatment suppresses answers.
• Routing changes. A new carrier route, or a failover, can change ASR overnight with no change on your side.
• Time-of-day and geography. ASR has a strong diurnal shape. Comparing a Monday morning to a Friday evening tells you nothing.

Because ASR blends all of these, a change in ASR alone is a symptom, not a diagnosis. The next two metrics separate the causes.

ACD — Average Call Duration

ACD is the mean duration of connected calls. Where AHT is an agent-workload measure, ACD is a conversation-quality proxy — and its distribution matters far more than its average.

The diagnostic pattern to look for:

A specific pattern worth alerting on: a rising cluster of connected calls under about six seconds. That is the signature of answer-and-hang-up behavior, which frequently indicates the recipient saw a spam label on their handset.

PDD — Post Dial Delay

PDD is the interval between the call being placed and ringing beginning. It is the most under-used of the three and the most diagnostic when it moves.

PDD is essentially a measure of signalling latency. Typical expectations vary by route and destination, but within a stable route it should be consistent. When it rises:

• Route changes. An extra hop, a new intermediate carrier, or a failover path will show up in PDD before it shows up anywhere else.
• Carrier congestion. Time-correlated PDD spikes that resolve on their own typically point upstream rather than at your configuration.
• Abandonment risk. High PDD in a progressive or predictive mode means the agent is connected and waiting, or the customer answers into silence. Both are expensive.

Long PDD combined with falling ACD is a particularly reliable indicator: the recipient answers, hears dead air because the connection took too long to establish, and hangs up.

Reading them together

A workable diagnostic sequence:

1. Segment before you compare. By campaign, list source, ANI group, destination region and hour of day. An aggregate ASR movement is often one segment moving and everything else flat.
2. Check PDD first. If PDD moved, the cause is very likely routing or carrier, and no amount of list or script work will help.
3. Then check the ACD distribution. Not the mean — the shape. Short-call clustering and long-tail growth have completely different causes.
4. Then check ASR by ANI group. If specific ANIs are underperforming while others on the same list are fine, it is a number-reputation problem, not a list problem.
5. Change one thing. With a defined measurement window. Simultaneous changes cannot be attributed afterwards, which is how teams end up with folklore instead of knowledge.

What to instrument

Most of this analysis is impossible after the fact if the data was never captured at the right grain. At minimum, retain per-attempt records carrying: timestamp, ANI used, destination region, route or trunk, disposition, PDD, ring duration, connect flag and call duration.

With that in place, the diagnostic sequence above takes minutes rather than days — and it becomes possible to alert on the patterns rather than investigate them.