Chapter Contents |
Previous |
Next |

The X11 Procedure |

**MONTHLY***options;*

The following options can appear in the MONTHLY statement:

**ADDITIVE**-
performs additive adjustments.
If the ADDITIVE option is omitted,
PROC X11 performs multiplicative adjustments.
**CHARTS= STANDARD****CHARTS= FULL****CHARTS= NONE**-
specifies the charts produced by the procedure.
The default is CHARTS=STANDARD, which specifies
12 monthly seasonal charts and a trend cycle chart.
If you specify CHARTS=FULL (or CHARTS=ALL), the
procedure prints additional charts of irregular
and seasonal factors.
To print no charts, specify CHARTS=NONE.

The TABLES statement can also be used to specify particular monthly charts to be printed. If no CHARTS= is given, and a TABLES statement is given, the TABLES statement overrides the default value of CHARTS=STANDARD; that is, no charts (or tables) are printed except those specified in the TABLES statement. However, if both the CHARTS= option and a TABLES statement are given, the charts corresponding to the CHARTS= option and those requested by the TABLES statement are printed.

For example, suppose you wanted only charts G1, the final seasonally adjusted series and trend cycle, and G4, the final irregular and final modified irregular series. You would specify the following statements:monthly date=date; tables g1 g4;

**DATE=***variable*-
specifies a variable that gives the date for each observation.
The starting and ending dates are obtained from the first and
last values of the DATE= variable, which must contain SAS date
values. The procedure checks values of the DATE= variable
to ensure that the input observations are sequenced correctly.
This variable is automatically added to the OUTPUT= data set
if one is requested and extrapolated if necessary.
If the DATE= option is not specified, the
START= option must be specified.

The DATE= option and the START= and END= options can be used in combination to subset a series for processing. For example, suppose you have 12 years of monthly data (144 observations, no missing values) beginning in January, 1970 and ending in December, 1981, and you only wanted to seasonally adjust six years beginning in January of 1974. Specifyingmonthly date=date start=jan1974 end=dec1979;

would seasonally adjust only this subset of the data. If, instead, you wanted to adjust the last eight years of data, only the START= is needed:monthly date=date start=jan1974;

**END=***mmmyyyy*-
specifies that only the part of the input series
ending with the month and year given be adjusted
(for example, END=DEC1970).
See the DATE=
*variable*option for using the START= and END= options to subset a series for processing. **EXCLUDE=***value*-
excludes from the trading-day regression any
irregular values that are more than
*value*standard deviations from the mean. The EXCLUDE=value must be between .1 and 9.9, with the default value being 2.5. **FULLWEIGHT=***value*-
assigns weights to irregular values based on
their distance from the mean in standard
deviation units. The weights are used for
estimating seasonal and trend cycle components.
Irregular values less than the FULLWEIGHT=
*value*(in standard deviation units) are assigned full weights of 1, values that fall between the ZEROWEIGHT= and FULLWEIGHT= limits are assigned weights linearly graduated between 0 and 1, and values greater than the ZEROWEIGHT= limit are assigned a weight of 0.

For example, if ZEROWEIGHT=2 and FULLWEIGHT=1, a value 1.3 standard deviations from the mean would be assigned a graduated weight. The FULLWEIGHT=value must be between .1 and 9.9 but must be less than the ZEROWEIGHT=value. The default is FULLWEIGHT=1.5. **LENGTH**-
includes length-of-month allowance in computing
trading-day factors. If this option is omitted, length-of-month
allowances are included with the seasonal factors.
**NDEC=***n*-
specifies the number of decimal places shown on the printed
tables on the listing. This option has no effect
on the precision of the variables values in the output data set.
**PMFACTOR=***variable*-
specifies a variable containing the prior monthly factors.
Use this option if you have previous knowledge of monthly
adjustment factors. The PMFACTOR= option can be used to:
- adjust the level of all or part of a series with discontinuities
- adjust for the influence of holidays that fall on different dates from year to year, such as the effect of Easter on certain retail sales
- adjust for unreasonable weather influence on series, such as housing starts
- adjust for changing starting dates of fiscal years (for budget series) or model years (for automobiles)
- adjust for temporary dislocating events, such as strikes

See "Prior Daily Weights and Trading-Day Regression" in the "Details" section later in this chapter for details and examples using the PMFACTOR= option. **PRINTOUT= STANDARD | LONG | FULL | NONE**-
specifies the tables to be printed by the procedure.
If the PRINTOUT=STANDARD option is specified,
between 17 and 27 tables are printed, depending on
the other options that are specified.
PRINTOUT=LONG prints between 27 and 39 tables,
and PRINTOUT=FULL prints between 44 and 59 tables.
Specifying PRINTOUT=NONE results in no tables being printed;
however, charts are still printed.
The default is PRINTOUT=STANDARD.

The TABLES statement can also be used to specify particular monthly tables to be printed. If no PRINTOUT= is given, and a TABLES statement is given, the TABLES statement overrides the default value of PRINTOUT=STANDARD; that is, no tables (or charts) are printed except those given in the TABLES statement. However, if both the PRINTOUT= option and a TABLES statement are given, the tables corresponding to the PRINTOUT= option and those requested by the TABLES statement are printed. **START=***mmmyyyy*-
adjusts only the part of the input series
starting with the specified month and year.
When the DATE= option is not used, the START= option
gives the year and month of the first input observation.
For example, START=JAN1966.
START= must be specified if DATE= is not given.
If START= is specified (and no DATE= option is given),
and an OUT= data set is requested, a variable
named _DATE_ is added to the data set, giving
the date value for each observation.
See the DATE=
*variable*option for using the START= and END= options to subset a series. **SUMMARY**-
specifies that the data are already seasonally
adjusted and the procedure is to produce
summary measures. If the SUMMARY option is omitted,
the X11 procedure performs seasonal adjustment
of the input data before calculating summary measures.
**TDCOMPUTE=***year*-
uses the part of the input series beginning with January of
the specified year to derive trading-day weights.
If this option is omitted, the entire series is used.
**TDREGR= NONE | PRINT | ADJUST | TEST**-
specifies the treatment of trading-day regression.
The value NONE omits the computation of the
trading-day regression. The value PRINT computes
and prints the trading-day regressions but does not
adjust the series. The value ADJUST computes and
prints the trading-day regression and adjusts
the irregular components to obtain preliminary
weights. The value TEST adjusts the final series
if the trading-day regression
estimates explain significant variation on the
basis of an
*F*test (or residual trading-day variation if prior weights are used). The default is TDREGR=NONE.

See "Prior Daily Weights and Trading-Day Regression" in the "Details" section later in this chapter for details and examples using the TDREGR= option.

If ARIMA processing is requested, any value of TDREGR other than the default TDREGR=NONE will cause PROC X11 to perform an initial pass (see the "Details" section and the PRINTFP option).

The signifigance level reported Table C15 should be viewed with caution. The dependent variable in the trading day regression is the irregular component formed by an averaging operation. This induces a correlation in the dependent variable and hence in the residuals from which which the F-test is computed. Hence the distribution of the trading day regression F-statistics differs from an exact F; see Cleveland and Devlin, 1980 for details. **TRENDADJ**-
modifies extreme irregular values prior
to computing the trend cycle estimates in
the first iteration.
If the TRENDADJ option is omitted, the trend cycle
is computed without modifications for extremes.
**TRENDMA= 9 | 13 | 23.**-
specifies the number of terms in the
moving average to be used by the procedure in estimating
the variable trend cycle component. The value of the
TRENDMA= option must be 9, 13, or 23.
If the TRENDMA= option is omitted, the procedure
selects an appropriate moving average.
For information concerning the number of
terms in the moving average, see U.S. Bureau of
the Census (1967).
**ZEROWEIGHT=***value*-
assigns weights to irregular
values based on their distance from the mean
in standard deviation units. The weights are
used for estimating seasonal and trend cycle
components. Irregular values beyond the standard
deviation limit specified in the ZEROWEIGHT= option are
assigned zero weights. Values that fall between
the two limits (ZEROWEIGHT= and FULLWEIGHT=)
are assigned weights linearly graduated between 0 and 1.
For example, if ZEROWEIGHT=2 and FULLWEIGHT=1,
a value 1.3 standard deviations from the mean
would be assigned a graduated weight.
The ZEROWEIGHT=value must be between .1 and 9.9 but
must be greater than the FULLWEIGHT=value.
The default is ZEROWEIGHT=2.5.

The ZEROWEIGHT option can be used in conjunction with the FULLWEIGHT= option to adjust outliers from a monthly or quarterly series. See Example 21.3 later in this chapter for an illustration of this use.

Chapter Contents |
Previous |
Next |
Top |

Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.