Seasonal Adjustment

Statistical procedure for time series data to remove seasonal variations, allowing a clearer view of nonseasonal changes in the data.

Adjustment for periodic swings in statistical data or changes in supply and demand. For example, the volume of bank debits (checks and check-like drafts, including Negotiable Order of Withdrawal accounts, written by businesses and consumers) is higher in December than the following month's total, due mostly to year-end holiday shopping. Seasonal adjustment would reduce the December number, while raising the January figure. If there is no change in trends, both numbers would be identical.