On Wednesday February 8, 2012, the world population passed 7 billion people. Or was it October 31, 2011 or March 12, 2012? How do we know the date so precisely? Nathan Keyfitz had a life-long fascination with different aspects of counting, estimation, and forecasting, especially in the context of producing such population figures and in census taking. Most demographers have traditionally viewed census taking as a counting exercise, but there has been a lively debate about combining counting with forms of estimation, and the precision that would result. In this presentation, I describe aspects of this debate, including Keyfitz's contributions to and perspectives on it.

1. I take my title from a 1978 National Research Council report, Counting the People in 1980: An Appraisal of Census Plans, authored by a panel chaired by Nathan Keyfitz.

Professor Steve Fienberg
Co-Founder of Journal of Privacy and Confidentiality, 2006, International Society for Bayesian Analysis, President 1996-1997; Past-President, 1998.
Chair, Selection Committee for the DeGroot Prize, 2001-2004.
Co-chair National Academy of Sciences, Report Review Committee, 2008-2012.
Thorsten Sellin Fellow of the American Academy of Political and Social Science, 2004.
Elected member of The National Academy of Sciences.
Elected fellow of Royal Society of Canada.
Elected fellow of the American Academy of Arts and Sciences.
Fellow of American Association for the Advancement of Science, American Statistical Association, Institute of Mathematical Statistics.