According to United Nations estimates, world population reaches the six billion mark on 12 October 1999. The World at Six Billion was prepared in response to the widespread global attention to this historic milestone. The World at Six Billion provides in tabular and graphic form salient characteristics of past, current and future world population growth. The publication is based largely on the publications and databases of the Population Division, including the official United Nations world population estimates and projections, prepared and biennially updated by the Population Division for the United Nations system.