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Definition: Smoothing

OECD - Data and Metadata Reporting

The process of removing fluctuations in an ordered series so that the result shall be "smooth" in the sense that the first level differences are regular and higher order differences small.

Although smoothing can be carried out by freehand methods, it is usual to make use of moving averages or the fitting of curves by least squares procedures. In fact, the concept is closely tied to that of trend fitting.
Marriott, F.H.C., 1990, "A Dictionary of Statistical Terms", 5th ed., Longman Scientific and Technical, Burnt Mill, Harlow, Essex, England, for the International Statistical Institute [quoted in Organisation for Economic Co-operation and Development (OECD), "Data and Metadata Reporting and Presentation Handbook", OECD, Paris, 2007]