Age at menarche: Nicolai Edvard Ravn's data on 3385 women in mid-19th century Denmark.
Medical observations on 3385 Danish women, from the 1840s, indicate that at that time the average age at menarche was 16 years and 3 months for Denmark as a whole. Since then, age at menarche has decreased, with an average rate of a little over 2 1/2 months per decade.
D000293:Adolescent; D000367:Age Factors; D003718:Denmark; D005260:Female; D049671:History, 18th Century; D006801:Humans; D008572:Menarche; D013997:Time Factors