X-11

X-11 was foor many years the most widely-used program for seasonal adjustment of monthly and quarterly time series. It was released by the U. S. Bureau of the Census in 1965. The name originally meant the 11th experimental variant of the Bureau's Census Method II program. Not all previous variants were released, only X-3, X-9 and X-10.

X-12 or X-12-ARIMA, a considerable improvement, was released in 1993, and has now mostly superseded x-11. X-13 or X-13-SEATS is now available.

Methodology

X-11 and its successors assume that any monthly and quarterly time series O (for original) can be decomposed into a smooth trend C (the letter refers to economic cycles), a seasonal pattern S and an irregular component I. It may treat the series as additive or multiplicative; the British variant, X-12 and X-13 also have a pseudoadditive model. These are respectively

• O = C + S + I
• O = C * S * I
• O = C * (S + I - 1)

The programs have an optional Section A to perform prior adjustments, for example to remove known distortions.

External links

• X-12 website

References

Seasonal Adjustment with the X-11 Method (Lecture Notes in Statistics) by Dominique Ladiray, Benoit Quenneville, and Allan Young, Pub. Springer-verlag (2001); ISBN 978-0387951713

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