20th century, such as the Iran–Iraq War, the Soviet–Afghan War, the second Sudanese civil war, the Korean War and the Vietnam war. It is estimated that traffic collisions caused the death of around 60 million people during the 20th century. Ageing population A natural population increase occurs when birth rates are higher than death rates. Recently and most notably, the years immediately after World War II saw an explosion in fertility rates called the Baby Boom because the returning soldiers and displaced people started new families. Death rates were significantly lower during the baby boom and thus populations increased substantially. Today these baby boomers are approaching old age and driving up the average age of the overall population. The World Bank predicts a dramatic decrease in population size from the increase in death rates over the next decade. Fertility rates and consequently live birth rates declined over the century, while age-adjusted death rates fell more dramatically. Children in 1999 were 10 times less likely to die than children in 1900. For adults 24–65, death rates have been halved. The death rate for Americans aged 65 to 74 fell from nearly 7% per year to fewer than 2% per year. Improvements in public health During the 20th century, an enormous improvement in public health led to an overall decrease in death rates. Infant mortality rates and maternal mortality rates have dramatically decreased. In the early 1900s, 6–9 women died in pregnancy-related complications for every 1,000 births, while 100 infants died before they were 1 year old. In 1999, at the end of the century, the infant mortality rate in the United States declined more than 90% to 7.2 deaths per 1,000 live births. Similarly, maternal mortality rates declined almost 99% to less than 0.1 reported deaths per 1,000 live births. There are a variety of causes for this steep decline in death rates in the 20th century: Environmental interventions Improvement in nutrition Advances in clinical medicine (sulfonamide in 1937, penicillin in the 1940s) Improved access to health care Improvements in surveillance and monitoring disease Increases in education levels Improvement in standards of living. Despite these tremendous decreases in infant mortality and maternal mortality, the 20th century experienced significant disparities between minority death rates compared to death rates for white mothers. In the 1900s, black women were twice as likely to die while giving birth compared to white women. Towards the end