Boys in the U.S. are entering puberty up to two years earlier than in previous decades, according to a study by the American Academy of Pediatrics. The trend is well documented and backed up by a large body of data, but the reasons for it remain unclear, as do the consequences for public health. African Americans enter puberty the earliest. Clinical data collected by pediatricians in 41 states show that in this ethnic group, 9-year-olds show signs of maturation. White boys enter puberty at an average age of 10, followed by the Latino minority at 10 and a half years. NEWS_MORE_BOX Average age was calculated based on the onset of “second stage pubic hair” observed by a pediatrician. According to study author Marcia Herman-Giddens, tracking changes in children’s growth and development is an important part of assessing a youth’s overall health. Until now, however, such data were missing. Parents need to know if their sons are maturing at appropriate age ranges, but until now, detailed and reliable data providing insight into national trends in the US have not been released. The study was published in the journal Pediatrics.