Secular variation

From Wikipedia, the free encyclopedia
Jump to: navigation, search

The secular variation of a time series is its long-term non-periodic variation (see Decomposition of time series). Whether something is perceived as a secular variation or not depends on the available timescale: a secular variation over a time scale of centuries may be part of a periodic variation over a time scale of millions of years. Natural quantities often have both periodic and secular variations. Secular variation is sometimes called secular trend or secular drift when the emphasis is on a linear long-term trend.


The term secular variation is used wherever time series are applicable in economics, operations research, biological anthropology, astronomy (particularly celestial mechanics) such as VSOP (planets) etc.


In astronomy, secular phenomena refers to long-term perturbations in the motion of planets. The precession of the Earth's axis has a period of 25,771.5 years, so on a much shorter time frame it appears to be a "drift" of the position of the equinox in the plane of the ecliptic of approximately one degree every 71.6 years.[1]

Market trends[edit]

Market trends are classified as secular, primary and secondary for long, medium and short time frames.[2] Some traders identify market trends using technical analysis.

Geomagnetic secular variation[edit]

Geomagnetic secular variation refers to changes in the Earth's magnetic field. The field has variations on time scales from milliseconds to millions of years, but rapid changes mostly come from currents in the ionosphere and magnetosphere. The secular variation is the changes over periods of a year or more, reflecting changes in the Earth's core. Phenomena associated with this secular variation include geomagnetic jerk, westward drift and geomagnetic reversals.[3]

Biological anthropology[edit]

A secular trend has been observed in the age of onset of puberty (menarche/first menstruation and beginning of breast development) of girls around the world beginning roughly 4 months earlier each decade. This is largely believed to be caused by nutritional changes in children over time.[4][5][6][7][8][9]


  1. ^ Lowrie, William (2004). Fundamentals of Geophysics. Cambridge University Press. ISBN 0-521-46164-2. 
  2. ^ Edwards, R.; McGee, J.; Bessetti, W. H. C. (2007). Technical Analysis of Stock Trends. CRC Press. p. 17. ISBN 978-0-8493-3772-7. 
  3. ^ Merrill, Ronald T.; McElhinny, Michael W.; McFadden, Phillip L. (1996). The Magnetic Field of the Earth: Paleomagnetism, the Core, and the Deep Mantle. International Geophysics Series 63. Academic Press. ISBN 9780124912458. 
  4. ^ Okasha, M; McCarron, P; McEwen, J; Smith, GD (2001). "Age at menarche: secular trends and association with adult anthropometric measures". Annals of Human Biology 28 (1): 68–78. doi:10.1080/03014460150201896. PMID 11201332. 
  5. ^ Wattigney, WA; Srinivasan, SR; Chen, W; Greenlund, KJ; Berenson, GS (1999). "Secular trend of earlier onset of menarche with increasing obesity in black and white girls: the Bogalusa Heart Study". Ethnicity & Disease 9 (2): 181–189. PMID 10421080. 
  6. ^ Prentice, S; Fulford, AJ; Jarjou, LM; Goldberg, GR; Prentice, A (2010). "Evidence for a downward secular trend in age of menarche in a rural Gambian population". Annals of Human Biology 37 (5): 717–721. doi:10.3109/03014461003727606. PMID 20465526. 
  7. ^ Rokade, Shrikant; Mane, Arati (2008), "A Study Of Age At Menarche, The Secular Trend And Factors Associated With It", The Internet Journal of Biological Anthropology 3 (2) 
  8. ^ Biro, Frank; Galvez, MP; Greenspan, LC; Succop, PA; Vangeepuram, N (Sep 2010), "Pubertal assessment method and baseline characteristics in a mixed longitudinal study of girls", Pediatrics 126 (3), PMID 20696727 
  9. ^ Euling, Susan; Herman-Giddens, Marcia; Lee, Peter; Selevan, Sherry (February 2008). "Examination of US Puberty-Timing Data from 1940 to 1994 for Secular Trends: Panel Findings". Pediatrics 121 (3).