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From left-skewness to symmetry: how body-height distribution among Swiss conscripts has changed shape since the late 19th century.

Research paper by Kaspar K Staub, Joël J Floris, Ulrich U Woitek, Frank F Rühli

Indexed on: 27 Aug '14Published on: 27 Aug '14Published in: Annals of human biology



Abstract

It is generally accepted that height distribution in modern populations is nearly symmetrical. However, it may deviate from symmetry when nutritional status is inadequate. Aim and subjects: This study provides an analysis of changes in the shape of the height distributions among Swiss conscripts (n = 267,829) over the past 130 years based on a highly representative, standardized and unchanged data source.The analysed distributions from the 1870s-1890s conscription years are markedly left-skewed (-0.76 to -0.82), with short and very short men significantly over-represented. Standard deviation is 7.7 cm. In particular, the left tails of the late-19th- and early-20th-century distributions are very heavy. In the first half of the 20th century the first signs of a diminution of the heavy left tail are observable, by the 1970s the phenomenon disappears and height distribution becomes symmetrical; standard deviation is now 6.5 cm.The relatively strong left-skewness during the late 19th and early 20th centuries may have been due to the interaction of a number of causes, chiefly malnutrition, a wider range in physical development at age 19 and widespread iodine deficiency.