Scalp hair length. II. Estimating the percentages of adults in the USA and larger populations by hair length
Robbins, C.; Robbins, M.G.
Journal of Cosmetic Science 54(4): 367-378
2003
ISSN/ISBN: 1525-7886 PMID: 14528389 Document Number: 557750
Scalp hair length assessments by anatomical site, previously made in Florida theme parks on adults, are related to anatomical measurements to obtain estimates of free-hanging hair lengths in centimeters. A plot of the natural logarithm of the percent population versus these hair lengths provides a straight line and an equation that permits the estimation of the numbers of persons in the USA and larger populations with hair lengths up to 183 cm (just beyond ankle-length). Data were also collected via a literature search for even longer hair lengths (ankle-length or longer) to provide an equation to estimate the numbers of persons with exceptionally long hair. A comparative plot of these two equations suggests that "normal" anagen periods may be considerably longer than current estimates in the literature.