Annotation consistency measures whether a single person, an annotator, a moderator, an agent, applies the same standard to similar items over time, rather than comparing how different people agree with each other. It's about whether the same person, looking at two nearly identical items on different days, would make the same call both times.

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‍Why it matters

This is a different problem than agreement between people, since two reviewers could agree with each other perfectly today while both quietly drifting away from their original standard over the following weeks. Fatigue, distraction, or simply forgetting a specific guideline detail can cause one person's own judgment to shift gradually, with no one else's influence involved at all. This kind of drift is harder to catch than disagreement between people, since there's no second opinion flagging it in the moment.

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‍How teams check it

Teams typically check this by quietly mixing a small number of previously completed items back into someone's current workload, then comparing the new answer against their own original one. A meaningful mismatch on the same item is a stronger signal of individual drift than any comparison against someone else's judgment, since it isolates exactly one variable: whether this person is still applying their own standard consistently.