Evidence grade

Every published entry carries an evidence grade: one word naming the strongest kind of source that stands behind its core claims. There are four, and they describe who did the looking, not how well the project went.

• Peer-reviewed — a finding published through academic peer review, as with London's Ultra Low Emission Zone.
• Independent — an examination by someone with no stake in the outcome: an audit office, a court, a research institute. Johannesburg's water losses are graded this way.
• Official — the operator's own reporting. The right source for what a system does, and the wrong one for whether it worked. Busan–Gimhae sits here.
• Media — press coverage, and also vendor and supplier material, which is marketing rather than measurement. LinkNYC is graded media.

Two things the grade is not. It is not a score for the project — a well-run system whose results only its operator has published is graded official, and a failure documented by a national audit office is graded independent. And where an entry states no impact figure at all, the grade describes the sourcing of the entry rather than the strength of a number, and the page says so in place.

The State of the Evidence counts these grades across the whole atlas, which is the only way to see how much of the smart-city record anyone outside the projects has actually examined.