Just as on the demand side, the position of the supply can shift, say from a change in the price of a productive input or a technical improvement. The Law of Supply states that, in general, a rise in price leads to an expansion in supply and a fall in price leads to a contraction in supply.
Puberty takes place over a number of years, and the age at which it starts and ends varies widely. It generally begins somewhere between the ages of 7 and 13 for girls, and somewhere between the ages of 9 and 15 for guys, although it can be earlier or later for some people.
Contrary to popular belief, it seems women may actually reach their sexual peak before men. According to a recent survey conducted by Atlanta-based sex toy manufacturer LoveHoney, women reach their sexual peak at age 26, while men peak later - at 32. The poll, which included 1,000 adults aged 18-65, defined 'peak' as the period where participants said they were having the 'best' sex of their lives.