The total force of mortality over the life course is usually composed of three phases: (1) decreasing trend during the first decade of life, (2) hump in the second and third decade, and (3) increasing trend thereafter, marked by a progressive deceleration in very old age. This aggregated evolution does not necessarily reflect the experience of risk in individuals. Area A1 represents senescent mortality between ages 10 and 30, and area A2 represents hump mortality after age 30