Signed-call coverage reaches 54.8% as prolific robocall signers keep A-level attestation

TransNexus published its August STIR/SHAKEN numbers on September 2. Signed calls at termination rose half a point to 54.8%, which the company calls the highest it has recorded “but far from the level needed to deliver the full benefits of call authentication.” Robocalls were 3.2% of all calls, down from 3.5% in July. Calls signed at A-level attestation held at 33.8%, B-level fell half a point to 5.7%, and C-level held at 8.0%.

Among the ten SHAKEN-authorized providers ranked highest by robocall percentage, 71% of signed calls carried A-level attestation and 27% carried C. Of the C-signed calls from that group, 69% were robocalls. The count of SHAKEN-authorized providers rose 1.6% over the month while the count of originating providers actually observed signing calls fell 0.1%.

The figures describe calls received by hundreds of voice service providers running TransNexus products — a sample of terminating traffic rather than the network. TransNexus has published the series monthly since April 2021, which makes it the longest continuous attestation record available to read against YouMail’s monthly index and the TNS annual report. A Branded Calling ID promotion sits in the middle of the attestation data.

A-level attestation means the signing provider vouches that the caller has the right to use the number. The ten providers signing the most robocalls apply it to 71% of their traffic.