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Introduction

Seasonal Adjustment

The X11 procedure provides seasonal adjustment of time series by using the Census X-11 or X-11 ARIMA method. The X11 procedure is based on the U.S. Bureau of the Census X-11 seasonal adjustment program and also supports the X-11 ARIMA method developed by Statistics Canada. The X11 procedure includes the following features:

  • decomposition of monthly or quarterly series into seasonal, trend, trading day, and irregular components

  • both multiplicative and additive form of the decomposition

  • all the features of the Census Bureau program

  • support of the X-11 ARIMA method

  • support of sliding spans analysis

  • processing of any number of variables at once with no maximum length for a series

  • computation of tests for stable, moving, and combined seasonality

  • optional printing or storing in SAS data sets of the individual X11 tables that show the various components at different stages of the computation; full control over what is printed or output

  • ability to project seasonal component one year ahead, which enables reintroduction of seasonal factors for an extrapolated series

The X12 procedure provides seasonal adjustment of time series using the X-12 ARIMA method. The X12 procedure is based on the U.S. Bureau of the Census X-12 ARIMA seasonal adjustment program (version 0.3). It also supports the X-11 ARIMA method developed by Statistics Canada and the previous X-11 method of the U.S. Census Bureau. The X12 procedure includes the following features:

  • decomposition of monthly or quarterly series into seasonal, trend, trading day, and irregular components

  • support of multiplicative, additive, pseudo-additive, and log additive forms of decomposition

  • support of the X-12 ARIMA method

  • support of regARIMA modeling

  • automatic identification of outliers

  • support of TRAMO-based automatic model selection

  • use of regressors to process missing values within the span of the series

  • processing of any number of variables at once with no maximum length for a series

  • computation of tests for stable, moving, and combined seasonality

  • spectral analysis of original, seasonally adjusted, and irregular series

  • optional printing or storing in a SAS data set of the individual X11 tables that show the various components at different stages of the decomposition; full control over what is printed or output

  • optional projection of seasonal component one year ahead, which enables reintroduction of seasonal factors for an extrapolated series

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