From stinchcd@mail.nih.gov Mon Jan 24 11:49:51 2005 Received: from mxe2.u.washington.edu (mxe2.u.washington.edu [140.142.33.14]) by lists.u.washington.edu (8.13.3+UW05.01/8.13.3+UW05.01) with ESMTP id j0OJnodm103626 for ; Mon, 24 Jan 2005 11:49:50 -0800 Received: from NIHHUBIMS.hub.nih.gov (nihhubims.hub.nih.gov [128.231.90.111]) by mxe2.u.washington.edu (8.13.3+UW05.01/8.13.3+UW05.01) with ESMTP id j0OJnm0P013701 for ; Mon, 24 Jan 2005 11:49:50 -0800 Received: by nihhubims.hub.nih.gov with Internet Mail Service (5.5.2658.27) id ; Mon, 24 Jan 2005 14:49:48 -0500 Message-ID: <16A0583FB1644E4DB8C0A0265028B6FD026BB65C@nihexchange13.nih.gov> From: "Stinchcomb, David (NIH/NCI)" To: waphgis@u.washington.edu Cc: "'dstinchcomb@compuvision.net'" Subject: Census Tract Data Conversions Date: Mon, 24 Jan 2005 14:49:44 -0500 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2658.27) Content-Type: text/plain X-Uwash-Spam: Gauge=IIIIIII, Probability=7%, Report='__C230066_P5 0, __CT 0, __CT_TEXT_PLAIN 0, __FRAUD_419_BADTHINGS 0, __HAS_MSGID 0, __HAS_X_MAILER 0, __IMS_MSGID 0, __IMS_MUA 0, __MIME_VERSION 0, __SANE_MSGID 0' We are looking into ways to convert data based on 1990 census tracts into data based on 2000 census tracts. With the aid of a GIS, we know we could do the conversion by assigning values proportional to the area of the census tract pieces (the intersection of the two layers). However, this assumes that the population is uniformly distributed across space and we are not comfortable with this assumption. There is a set of "Census Tract Relationship Files" put out by the Census Bureau: http://www.census.gov/geo/www/relate/rel_tract.html These files seem to provide enough information to allow such a conversion based on the actual population in each piece rather than the area. Has anyone used these relationship files to do population-based conversions of 1990 census tract data to 2000 census tract data? If so, can you share any of the procedural details? In any case, let me know if you think this would be a useful tool. I will summarize responses. Thanks, -- Dave Stinchcomb Health Statistician / Geographer National Cancer Institute StinchcD@mail.nih.gov 301-594-7251 .