Benchmark Revision

A benchmark revision is a periodic overhaul of an entire statistical series rather than an update to one period. The agency re-anchors the series to a more complete source — a census, a full tax or employment register, a new classification of industries — and may change the base year, the weights or the methodology at the same time. Values going back years can move as a result. These revisions are announced in advance and documented, because they break comparability with everything computed before them. A model, a spreadsheet or a rule written against the old vintage of a series keeps running afterwards and quietly means something different; and a level shift on a long chart is often a benchmark revision rather than an event in the economy. The agency's methodology note is what tells the two apart.