Seasonally Adjusted

Plain-English definition. A seasonally adjusted series is an original statistical series after recurring calendar and seasonal effects have been estimated and removed. It can make one month or quarter easier to compare with the next.

What is removed. Seasonal effects are systematic patterns linked to the calendar. Examples include Christmas spending, the number of trading days in a month and holidays such as Easter that move between months. The adjustment aims to stop those recurring patterns from hiding other movements in the data.

What remains. Seasonal adjustment does not remove every unusual event or data error. A seasonally adjusted estimate still contains irregular short-term influences. An unexpected weather event, industrial dispute or one-off transaction can still move the result.

Original, seasonally adjusted and trend. Original estimates are the figures produced from the source data before seasonal effects are removed. Seasonally adjusted estimates remove estimated calendar-related effects. Trend estimates also smooth irregular movements and are generally better for describing the underlying direction of a series. Keep the label when quoting a number because the three measures can differ.

Illustrative example. Suppose an original series regularly rises each December because of a recurring holiday pattern. Seasonal adjustment estimates that usual December effect and removes it. If the seasonally adjusted series still rises, the change is larger than the estimated recurring pattern. This example explains the method only and is not an official ABS series.

Why estimates are revised. The ABS often uses concurrent seasonal adjustment, which re-estimates seasonal factors when new monthly or quarterly data arrives. Recent seasonally adjusted and trend figures can therefore change in later releases. A revision does not automatically mean the previous release was wrong.

When comparing property, lending or construction data, match the reference period, unit and adjustment. Do not compare an original figure with a seasonally adjusted figure as if they were the same series. The Australian Market Data dashboard keeps each source date and label with the relevant measure.

Sources. ABS: Time Series Analysis, The Basics and ABS: Methods, Four pillars of labour statistics, checked 1 September 2026.

This entry provides general statistical information only. It is not a forecast, financial advice, credit advice or a statement that a seasonally adjusted movement will continue.

Last updated: 1 September 2026.