At the UN Population Division I led the team that prepared the official United Nations World Population Prospects and the World Urbanization Prospects. I was responsible for the publication of the 2006 Revision and the preparation and publication of the 2008 and 2010 Revisions of the World Population Prospects. I also led most of the preparation for the 2012 Revision, before I retired in February 2013. I also supervised, and contributed to, the preparation and publication of the 2007, 2009 and 2011 Revisions of the World Urbanization Prospects.
Under my leadership the Population Estimates and Projections Section of the Population Division introduced several new methods for population estimation and projection - most notably the first Probabilistic Population Projections for all countries of the world, published in 2012. For the high- and medium-fertility countries these projections are based on a Bayesian Hierarchical Model, which takes into account the empirical evidence of all fertility declines to calculate thousands of trajectories for the fertility decline of a particular country. This allows the calculation of confidence intervals for the projections. For details, please see the official website of the United Nations Population Division at:
I have also developed software and websites for many decades.