Hi! Elizabeth, Please check the information here to see if it can clarify your question: http://www.federalregister.gov/articles/2010/08/24/2010-20808/proposed-u rban-area-criteria-for-the-2010-census "All proposed criteria based on land area, population, and population density, reflect the information contained in the Census Bureau's Master Address File/Topologically Integrated Geographic Encoding and Referencing (MAF/TIGER) Database (MTDB) at the time of the initial delineation. All calculations of population density include only land; the areas of water contained within census tracts and census blocks are not used to calculate population density." Thanks! Juyin Chen, AICP Senior Modeling Systems Analyst Virginia Department of Transportation Transportation & Mobility Planning Division Office: (804) 225-3564 Fax: (804) 225-4785 Website: http://www.virginiadot.org/vtm/ <http://www.virginiadot.org/> ________________________________ From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Elizabeth Hassett Sent: Friday, May 20, 2011 2:04 PM To: ctpp-news(a)chrispy.net Subject: [CTPP] Census population density calculations Hello all, I am finding discrepancies between population densities that I'm calculating in ArcGIS using Census 2010 population data and the TIGER geography shapefiles (in my case for the county and state level), and population density numbers posted on Census websites. The discrepancy is from the square mileage calculation, in particular. Does anyone know if this is because water bodies are subtracted from the total square mileage for the density calculation (or if there is another reason for the discrepancy)? Thank you, Elizabeth Elizabeth Hassett Syracuse Metropolitan Transportation Council 100 Clinton Square 126 N. Salina Street, Suite 100 Syracuse, NY 13202 ehassett(a)smtcmpo.org (P) 315-422-5716 (F) 315-422-7753 Elizabeth Hassett Syracuse Metropolitan Transportation Council 100 Clinton Square 126 N. Salina Street, Suite 100 Syracuse, NY 13202 ehassett(a)smtcmpo.org (P) 315-422-5716 (F) 315-422-7753