Catherine Hood Consulting

Our frequently asked questions are divided into the following categories:


Do you have questions not answered here? Please send suggestions for other questions to "faq" at cchhood.com.

Please also see the Seasonal Adjustment Glossary.

Trouble-Shooting FAQ

  1. What do I do if I can't get X-12/X-13 to run?
  2. What do I do if I can't get X-12/X-13 installed?
  3. How can I get X-12/X-13 to run for my short series?
  4. How can I get X-12/X-13 to run for my weekly series?
  5. What do I do if I click on a spec file and I get an error message?

1. What do I do if I can't get X-12/X-13 to run?

If you are not using the Windows interface to X-12 or X-13, you should download this program. X-12-ARIMA and X-13ARIMA-SEATS is a DOS program, and it will not run if you simply double-click on an X-12/X-13 input file.

If you are running the latest version of the interface and it doesn't load, it could be a sign that you've changed the directory where the program is. If you want to move the program, you should probably reinstall the program.


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2. What do I do if I can't get X-12/X-13 installed?

Downloading what you need to download can be a bit overwhelming with all the available information on the US Census Bureau web site. To simplify the process, we have written some detailed downloading instructions that you can access here.


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3. How can I get X-12/X-13 to run for my short series?

The minimum length to seasonally adjust a time series in X-12 or X-13 is four years. However, there is something we can do for short series.

Seasonal adjustment can be difficult under the following conditions:

  • The trend is not approximated by a straight line.
  • Trading day and moving holiday regressors are present.
  • Outliers (level shifts or point outliers) are present.

Fortunately, if we have a short series that is fairly well-approximated by a straight line, and if we don’t need to estimate trading day, moving holidays, or outliers, then we can do a simple seasonal adjustment in Excel. The good news is that for short series, we probably can estimate the trend fairly well with a straight line. With only a few data points for a particular month or quarter, we don’t have enough data to estimate trading day or moving holiday effects anyway, so we won’t try to estimate them.

I've outlined the steps to compute a seasonal adjustment, with examples, in the paper (in PDF) "Seasonal Adjustment for Short Time Series in Excel."


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4. How can I get X-12/X-13 to run for my weekly series?

Unfortunately, X-12/X-13 can not compute seasonal adjustments for weekly series, and at this time, there is no widely accepted software that will compute adjustments for weekly time series.


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5. What do I do if I click on a spec file and I get an error message?

Again, please remember that X-12/X-13 is a DOS program, and it will not run if you simply double-click on an X-12/X-13 input file. However, a spec file should be a text file, so when you double-click on it, it is often useful for it to open in your favorite file editor. If this doesn't happen, it is because the .spc file extension is already associated with another program on your computer.

One solution is to open the text editor (NotePad, PFE, etc.) first and then open the spec file from the editor. However, many of us find it more convenient to be able to double click on the file name in Windows Explorer.

If you want to change the software associated with a file type, it is possible to right-click on one of the .spc files, and then click "Open With". (If "Open With" does not appear as a choice, click "Open".) From this window, select the text editing program you would like to use to open this file automatically. Select the "Always use the selected program to open this kind of file" check box, and then click OK.

You can use these steps for all the different kinds of X-12/X-13 input, output, and save files. If the file type doesn't have another program associated with it yet, you can click on New Type instead of Edit.


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Page design by David Joyce
FAQ written by Catherine C.H. Hood
with help from Lynn Imel, Kathy McDonald-Johnson, David Findley, Brian Monsell, and James Ashley
Copyright 2006-2017
Last modified: 7 Aug 2017