Tell me, what do you measure? Changes shipped? Lines of code? Customer satisfaction? Defect rate? MTTR? New engineer onboarding time/TTFC? Security/compliance audit turnaround time? Uptime? Employee retention? Rollback/forward-fix rates? Linter errors? Test coverage? Meaningful test coverage?

Depends on the clients maturity, but some places all of the above.

What are the numbers you are getting?