1. Social Science Research Institute and Population Research Institute, The Pennsylvania State University, University Park, PA, USA
2. CyberGIS Center for Advanced Digital and Spatial Studies, University of Illinois at Urbana-Champaign, Urbana, IL, USA
3. Department of Geography and Geographic Information Science, University of Illinois at Urbana-Champaign, Urbana, IL, USA
4. Department of Agricultural Economics, Sociology and Education, The Pennsylvania State University, University Park, PA, USA