1 Robert M. Groves is the Gerald Campbell, S.J. Professor, Department of Mathematics and Statistics and Department of Sociology, and is provost at Georgetown University, Washington, DC, USA. He is a former director of the Census Bureau. bgroves@georgetown.edu.
2 Steven H. Murdock is the Allyn R. and Gladys M. Cline Professor in Sociology, Rice University, Houston, TX, USA, and is a former director of the Census Bureau. steve.h.murdock@rice.edu.