The US Census Bureau reported that the 6 billionth person was born at 1.24 am on Sunday July 18, 1999. The United Nations however, had set that landmark at October 12, 1999.
Every second 5 people are born and 2 people die, a net gain of 3 people. At this rate, the world population will double every 40 years and would be 12 billion in 40 years, 24 billion in 80 years, and more than 48 billion in 120 years. However the United Nations estimate that world population will stabilize at 12 billion in 120 years, citing that effective family planning will result in a universally low birth rate. Education plays a key role: almost half of the 6 billion people are under age 25.
At the beginning of the second millennium (1000 AD) the world population was 400 million. In 1750 there were about 800 million people in the world. In 1850 there were a billion more, and by 1950, another billion. Then it took just 50 years to double to 6 billion. In another 50 years the world population is expected to be 9 billion, which means that a decrease in growth of the world population is expected.
The recent global population explosion is not only the consequence of increased birth rates but also the result of an unprecedented decrease in death rate. Significant advances in public health and medicine, phenomenal agricultural yields and the expanding global economy contributed to the population explosion as the lifespan average continues to increase.
Only one in ten people lived in cities in 1900. By 1994 the figure had grown to one of every two people, creating megalopolies of millions to tens of millions inhabitants. More than 400 cities have a population of more than a million people. Managing such large cities, and better management of the planet's resources, could become the most difficult problem of this century.
In spite of the population increase and desertification, famines have actually become less frequent in the past 200 years. The famines in Africa seen on TV are due to the political strife and civil wars (see current conflicts between countries) that disorganize the economy, paralyze transportation, and prevent emergency food drops. In fact, out of the 40 poorest and hungriest nations on earth, 36 actually export food to richer countries.