LGA anchoring explained Demographic Concept

Referenced by 4 other explainers

LGA anchoring is how Place Forecast keeps small-area estimates in line with published ABS totals for the LGA.

Place Forecast starts with small-area estimates. It then checks each category against the ABS total for the whole LGA. The small-area estimates may not add up to the ABS LGA figure. When they do not, Place Forecast scales them so the category total matches the ABS figure.

Small gaps can still show up between totals and category sums. This is because the ABS changes small Census counts to protect privacy. This is called perturbation. Place Forecast anchors on the category figures so each category matches the ABS total. It lets the page total carry the gap.

Sometimes a small-area count is missing or too small to trust. A count under four may be mostly noise from perturbation. In these cases Place Forecast keeps the reliable values and spreads the rest of the LGA figure across the uncertain areas, based on each area's overall size for that topic. If the reliable values already add up to more than the LGA figure, they are scaled down and the uncertain areas show zero.

LGA anchoring does not make each small-area value an exact ABS count. Small-area figures are still estimates. Use them to see patterns across the LGA. Do not read them as direct ABS counts.