Understanding the demographic changes that are likely to unfold over the coming years, as well as the challenges and opportunities that they present for achieving sustainable development, is important for designing and implementing the post-2015 development agenda. The 2015 Revision of World Population Prospects is the twenty-fourth round of official United Nations population estimates and projections that have been prepared by the Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat. The 2015 Revision builds on the previous revision by incorporating additional results from the 2010 round of national population censuses as well as findings from recent specialized demographic and health surveys that have been carried out around the world. The 2015 Revision provides the demographic data and indicators to assess population trends at the global, regional and national levels and to calculate many other key indicators commonly used by the United Nations system.