The importance of early and repeated assessments of pubertal maturation is also relevant to consideration of the relatively low internal consistency of the measure of pubertal timing for girls. The phrasing of some of the questions assessing pubertal maturation and physical development asked respondents to compare their physical development to when they were in grade school (up to 10 years old). Recent estimates indicate that the mean age of onset of breast development in the United States is now approximately 10 years in Caucasian girls and less than 9 years in African American girls (Herman-Giddens et al., 1997). Thus, while the mean age of menarche remains approximately 12 years old, many girls in the present study likely experienced the development of other pubertal characteristics in grade school. Variation in the pace of development of different features of pubertal maturation may have affected the reliability of the pubertal timing measure (Ge et al., 2007).
