Results:

Data were available for 50 countries. In 1955, mortality was highest in the 1- to 4-year age group. Mortality in children ages 1-9 years declined by 80-93% in the 50 years up to 2004, due largely to steep declines in mortality from communicable diseases. All-cause mortality also declined by 68-78% in young people ages 10-14 years in OECD, Central and South American, and other countries. Smaller declines (41-48%) were observed among young men (15-24 years). In 2000-04, mortality in people ages 15-24 years was higher than that in children ages 1-4 years in most countries studied, with the exception of some very low income countries. Mortality in young men (15-24 years) was 2-3 times higher than that in boys (1-4 years). Mortality among young women (15-24 years) was equal to that of young girls (1-4 years) from 2000 onwards. Substantial declines in death caused by communicable diseases were seen in all age groups and regions, although communicable and noncommunicable diseases remained the main causes of death in children (1-9 years) and young women (10-24 years). Injury was the dominant cause of death in young men (10-24 years) in all regions by the late 1970s. Improvements in mortality in young people ages 15-24 years were half that in children, due largely to static or rising injury-related mortality, particularly in young men. Violence and suicide became increasingly important causes of death in young people in the second half of the 20th century, together making up a quarter to a third of mortality in young men ages 10-24 years in all regions by 2000-04.