Other providers stamp fixed high/medium/low labels on news. We measure what actually happened in the market after each release and check the tier against it. When a supposedly critical event moves less than its label, we see it. When a second-tier event moves the market more, we see that too.
Example: USD CPI moved markets far harder in 2022, at the height of the inflation scare, than in the years since. It still moved them almost every time, which is why it stays at the top of our scale.
Where measured market reactions disagree with the raw calendar label, the REVDEN tier follows the measurement; elsewhere it starts from that label. Anything that consumes REVDEN news data automatically picks up the current classification. No manual maintenance needed.
Basis: thousands of releases graded over several years, recalculated regularly.