Contents
Is seasonal adjustment used?
Seasonal adjustment is widely used in official statistics as a technique for enabling timely interpretation of time series data. The purpose of seasonal adjustment is to remove systematic calendar-related variation associated with the time of the year, that is, seasonal effects.
How does seasonal adjustment work?
Seasonal adjustment is a statistical technique that attempts to measure and remove the influences of predictable seasonal patterns to reveal how employment and unemployment change from month to month. As a general rule, the monthly employment and unemployment numbers reported in the news are seasonally adjusted data.
What is the difference between seasonally adjusted and not seasonally adjusted?
Seasonal effects reflect typical movements in time series data due to established seasonal patterns; Seasonally adjusted data (which remove the seasonal component and the other calendar effects) are influenced by more than changes in the trend-cycle.
How does seasonal adjustment affect the original series?
The original (not seasonally adjusted) series increases, but the seasonally adjusted series shows a decrease. What does this discrepancy mean? What kinds of effects does seasonal adjustment remove and what kinds of effects does it not remove? What are the components of a time series that result from seasonal adjustment?
How is seasonal adjustment used in the CES?
Seasonal adjustment eliminates the part of the change attributable to the normal seasonal variation and makes it possible to observe the cyclical and other nonseasonal movements in CES State and Area series. Seasonally adjusted series are published monthly for selected nonfarm payroll employment estimates.
What kind of moving average is used for seasonal adjustment?
A 9, 13 or 23 term Henderson moving average is applied to the seasonally adjusted values, depending on the volatility of the series (a more volatile series requires a longer moving average), to produce an improved estimate of the trend.
How does seasonal adjustment work in the BLS?
If a historical correction is issued to the unadjusted supersector or sector series prior to the standard five year replacement period, seasonally adjusted data will be revised back to the earliest historically corrected year. The aggregation method of seasonally adjusted data is based upon the availability of underlying industry data.