The number of children per family, the sharing of beds and closets, hair washing habits, local customs and social contacts, healthcare in a particular area (e.g. school), and socioeconomic status were found to be significant factors in head louse infestation.[citation needed] Children between 4 and 13 years of age are the most frequently infested group.[30] In the U.S., African-American children have lower rates of infestation.[11]