Referenced by 13 other explainers
LGA anchoring is how Place Forecast lines up its small-area figures with ABS-published LGA totals for Census-based markers.
Each per-group figure at the LGA level matches the ABS figure. We get there in two steps. First, we add up the mesh-block values inside the LGA. Then we scale each group so its sum matches the ABS LGA figure for that group.
The page total can differ from the ABS total by a few people, homes, or families. The size of the gap depends on the marker. That small gap is perturbation. ABS perturbs each cell on its own. So the published total can differ a little from the sum of its category cells. We anchor on the per-group figures so each group matches ABS. We let the total carry the gap.
Sometimes ABS shows a non-zero figure for a group, but every small area in the LGA sits within ABS perturbation noise (a count under 4). When that happens, Place Forecast spreads the LGA value across the small areas. The split uses each area's natural base for the marker, such as total people for religion or total families for family markers. That way the group still shows, and the share each small area gets reflects the size of its plausible-hiding pool, not an even split. A like rule applies inside a small area when its mesh-block values are all noise. The marker page footnotes which groups carry this fallback for the LGA you are viewing.
The First Nations marker opts out of this spread. When every small area in the LGA sits within ABS perturbation noise for an Aboriginal or Torres Strait Islander group, Place Forecast does not make up a value at the small-area level, in line with Indigenous Data Sovereignty rules. For those groups, the small-area sum sits below the ABS LGA total. Treat the ABS LGA total as the more reliable figure.
Per-small-area figures are estimates. They are not scaled to ABS on their own. Only the LGA total per group is anchored. Use small-area figures to read shape and trend across an LGA, not as direct ABS counts.