STIR/SHAKEN statistics from August 2023

The August 2023 STIR/SHAKEN and robocall statistics are now available. The data show the latest trends in robocalls, STIR/SHAKEN participation and attestation level usage.

We’ve been publishing monthly STIR/SHAKEN statistics since April 2021. These numbers are gathered from well over a hundred voice service providers using our STIR/SHAKEN and robocall prevention solutions. The data describe calls they received from 842 other voice service providers that originated calls, including some robocalls, signed with STIR/SHAKEN.

Many robocalls are signed with B or C attestation

Robocalls signed with B attestation remain high, C attestation down

Line chart comparing robocall attestations over 6 months

Figure 1. Signed Robocalls by Attestation Last 6 Months

Figure 1 shows robocalls by attestation level over the past six months. Notice that robocalls signed with B- or C-level attestation were much higher than the robocall percentage for all calls. The percentage of robocalls among calls signed with C-level attestation dropped from 20.0% in July to 16.2% in August. The percentage of robocalls among calls signed with B-level attestation has been hovering around the 22%–23% range, settling at 21.2% in August.

STIR/SHAKEN participation

We measure STIR/SHAKEN participation changes in two ways:

  1. The number of Originating Service Providers (OSPs) signing calls received by our customers,
  2. Service providers authorized to do SHAKEN by the STI Policy Administrator (STI-PA),

SHAKEN signing up slightly

line chart showing the number of originating providers sending signed calls

Figure 2. Monthly Number of OSPs Sending Signed Calls

Figure 2 shows the number of Originating Service Providers (OSPs) signing calls. We observed 17 new SHAKEN signers in August.

The number of SHAKEN-authorized providers increases slightly

line chart showing an increase in SHAKEN participation

Figure 3. STIR/SHAKEN Authorized Providers by Month

Figure 3 shows the number of SHAKEN authorized providers. As with OSP signers, this number has an upward trend that has been increasing in recent months. There were 28 new SHAKEN authorized providers in August, a 2% increase from July.

These two measures show that the STIR/SHAKEN participation had a modest improvement.

STIR/SHAKEN coverage

STIR/SHAKEN call authentication will be more useful as the percentage of signed calls received at termination and calls with full A-level attestation increases. We had been observing slow, steady improvement over the past six months, but surprisingly, both measures of coverage were down in August.

Signed calls at termination down

line chart showing the percentage of signed calls received at termination

Figure 4. The Percentage of Signed Calls at Termination Last 6 Months

Figure 4 shows the percentage of signed calls at termination for the past six months. This figure had been slowly increasing, reaching 34% in July. Surprisingly, this number dropped from 33.9% in July to 31% in August.

Calls with full attestation down

line chart showing the percentage of calls received at termination by attestation level

Figure 5. Percentage of Calls with SHAKEN Attestation Levels Last 6 Months

Figure 5 shows that the percentage of calls signed with full attestation had been climbing over the past six months, reaching 24.5% in July. However, this figure dropped 3% to 21.5% in August.

bar chart on a computer

Patterns among prolific robocall signers

Here are robocall and attestation statistics for the top 10 SHAKEN-authorized providers ranked by the percentages of signed calls identified as robocalls.

Prolific robocall signers increase robocalls among A-level attestation calls

robocalls among calls with A-level attestation are increasing

Figure 6. Robocall Percentage by Attestation—Prolific Robocall Signers by Robocall %

Figure 6 shows that the robocall percentage of calls signed with full A-level attestation increased in August to its highest level in six months. Robocalls among calls signed with C-level attestation continue their downward trend.


  • Robocalls signed with B-level attestation remain high, while robocalls signed with C-level attestation improved slightly.
  • STIR/SHAKEN participation improved slightly.
  • STIR/SHAKEN coverage had been improving gradually but unexpectedly dropped in August.
  • Robocall percentages among the top 10 prolific robocall signers were up among A- and B-level attestation calls.

Note: We removed some of the charts used in previous STIR/SHAKEN statistics blog posts from this edition to focus on the charts we thought were best suited to follow the key trends in STIR/SHAKEN and robocalls.

TransNexus solutions

TransNexus is a leader in developing innovative software to manage and protect telecommunications networks. The company has over 25 years’ experience in providing telecom software solutions including toll fraud prevention, robocall mitigation and prevention, TDoS prevention, analytics, routing, billing support, STIR/SHAKEN and SHAKEN certificate services.

Contact us today to learn more.

Request information

* required

This information will only be used to respond to your inquiry. TransNexus will not share your data with any third parties. We will retain your information for as long as needed to retain a record of your inquiry. For more information about how we use personal data, please see our privacy statement.