Two official instruments rarely land on the same residual tick. Sample frames, edit rules, top-coding, and fee definitions move the mark even when the population looks familiar. Rule Mark treats those limits as part of the reading, not as footnotes to discard.
Coverage and edit rules
Household surveys miss some informal spells; administrative files miss some non-filers. Imputation and suppression rules can shift a published average without a change in underlying pay. Technical manuals list those steps; notes here point to them when a figure is quoted.
Comparing without collapsing
Side-by-side tables invite false precision. This desk keeps instruments named, windows dated, and contested claims labeled. The staff rule is a metaphor for measurement—not a tool for planning anyone’s secondary earnings. Corrections: support@rulemark.online.