Previous Page | Next Page

The X12 Procedure

ADJUST Statement

ADJUST options ;

The ADJUST statement adjusts the series for leap year and length-of-period factors prior to estimating a regARIMA model. The "Prior Adjustment Factors" table is associated with the ADJUST statement.

The following option can appear in the ADJUST statement.


specifies length-of-month adjustment, length-of-quarter adjustment, or leap year adjustment. PREDEFINED=LOM and PREDEFINED=LOQ are equivalent; the actual adjustment is determined by the interval of the time series. Also, since leap year adjustment is a limited form of length-of-period adjustment, only one type of predefined adjustment can be specified. The PREDEFINED= option should not be used in conjunction with PREDEFINED=TD or PREDEFINED=TD1COEF in the REGRESSION statement or MODE=ADD or MODE=PSEUDOADD in the X11 statement. PREDEFINED=LPYEAR cannot be specified unless the series is log transformed.

If the series is to be transformed by using a Box-Cox or logistic transformation, the series is first adjusted according to the ADJUST statement, then transformed.

In the case of a length-of-month adjustment for the series with observations , each observation is first divided by the number of days in that month, , and then multiplied by the average length of month (30.4375), resulting in . Length-of-quarter adjustments are performed in a similar manner, resulting in , where is the length in days of quarter .

Forecasts of the transformed and adjusted data are transformed and adjusted back to the original scale for output.

Previous Page | Next Page | Top of Page