Why SDG health indicators are harder to measure than they look

Surveillance systems are meant to support public health action, not just count events.

Completeness and timeliness alone are not reliable stand-alone checks of surveillance quality.

HIV incidence can be estimated by longitudinal follow-up, indirect models, or recent-infection testing.

NCD progress is often slow and uneven, so short-term measurement can mislead.

Maternal mortality estimates often need model-based correction because routine data can be incomplete, underreported, or misclassified.