Hair care
Scalp hair grows, on average, at a rate of about 1.25 centimeters per month, and shampoos or vitamins have not been shown to noticeably change this rate. Hair growth rate also depends upon what phase in the cycle of hair growth one is actually in; there are three phases. The speed of hair growth varies based upon genetics, gender, age, hormones, and may be reduced by nutrient deficiency (i.e., anorexia, anemia, zinc deficiency) and hormonal fluctuations (i.e., menopause, polycystic ovaries, thyroid disease).
Big hair
Many people of various ethnicities throughout the world have naturally voluminous hair. For these people, "big hair" is not a deliberate fashion statement requiring any particular technique to achieve, but rather the default state of their hair. Some 60 percent of the world's population has naturally curly hair, which tends to be more voluminous than straight hair.