CONTENTS DATA DESCRIPTION VARIABLES DATA RESTRICTIONS CITATION DATA ERRORS, CORRECTIONS AND QUALITY ASSESSMENT NO WARRANTY OR LIABILITY QUESTIONS ACKNOWLEDGEMENTS DATA DESCRIPTION U.S. Population Grids (Summary File 3), 2000: Alabama, Louisiana, and Mississippi (alpha version) This archive contains an ArcInfo workspace with grids of demographic data from the year 2000 census. The grids cover the states Alabama, Louisiana, and Mississippi for the set of variables described below. The grids are stored in geographic coordinates with the following parameters: Projection: Geographic Spheroid: WGS84 Datum: NAD83 Units: Decimal Degrees The grids have a resolution of 30 arc-seconds (0.0083 decimal degrees), or approximately 1 square km. The gridded variables are based on census block and census block group geography from Census 2000 TIGER/Line Files and census variables (income, poverty status, educational attainment, and housing variables) from Summary File 3. Census block group data are allocated to census blocks using variables from Summary File 1 (see below for more information). For more details on these sources see: Census 2000 TIGER Line Files: http://www.census.gov/geo/www/tiger/tigerua/ua_tgr2k.html Summary File 1: http://www.census.gov/Press-Release/www/2001/sumfile1.html Summary File 3: http://www.census.gov/Press-Release/www/releases/archives/census_2000/000548.html The Summary File 3 variables are transformed from census block groups to census blocks using a proportional allocation based on an appropriate variable from Summary File 1. For Summary File 1 variables, the census block is smallest geographical unit for which data are reported. For Summary File 3 variables, the smallest reporting unit is census block group. To transform census block group data to census blocks, the proportion of the census block group's Summary File 1 variable in each census block is calculated. This proportion is multiplied by the Summary File 3 variable to determine a value for each census block. For instance, the Summary File 1 variable used for the educational attainment variable is the population age 25 and older. If a census block contains 50% of the block group's population age 25 and older as reported in Summary File 1, that census block is allocated 50% of the census block group's population with an education attainment level of a high school degree or less, as reported in Summary File 3. The Summary File 1 variable used to allocate each variable is described below. Once the variables have been transformed to census blocks, they are transformed to a quadilateral grid using proportional allocation. An explanation of proportional allocation is available at: http://sedac.ciesin.columbia.edu/plue/gpw/index.html?whatisagrid.html&2 VARIABLES All variables are stored as counts (i.e., number of persons), one per grid. For the easy calculation of density grids, a land area grid is included. To create a density grid (per square kilometer), simply divide a count grid by the land area grid. To create a percentage grid, divide a count grid by the count grid that represents the universe for that variable. For example, to calculate the percentage of housing units without a vehicle, divide the number of occupied housing units without a vehicle by the total number of occupied housing units. Certain variables, including population, number of households, and number of housing units are gridded in both the U.S. Population Grids (Summary File 1), 2000 and the U.S. Population Grids (Summary File 3), 2000. The values for the two sets of grids will not be identical. The U.S. Population Grids (Summary File 1), 2000 are based on data from the Census 2000 short form. These data are collected for all households in the country. The U.S. Population Grids (Summary File 3), 2000 are based on the Census 2000 long form, which was completed by approximately one in six households. The population totals in Summary Files 1 and 3 are not identical. A full explanation of the differences is available at: http://factfinder.census.gov/home/en/epss/sf3_compare.html When calculating the percentage of the population with a given Summary File 3 variable, use the correct Summary File 3 variable as the denominator. Using the Summary File 1 variable may result in values of more than 100%. Variable descriptions by grid name: Population GCPOP300G Population counts GCP2500G Population age 25 and older GCPVP00G Population for whom the poverty level is determined GCHH300G Number of households Income GCSEVP00G Population living at less than 50% of the poverty level GCPOV00G Population living below the poverty level GCLOWI00G Population living at less than 200% of the poverty level GCAHHI00G Aggregate household income in 1999 Education GCEDU00G Population age 25 and older with a high school degree or less as their maximum level of educational attainment Housing GCHU300G Housing units GCOCC300G Occupied housing units GCHUNV00G Occupied housing units without a vehicle GCHA100G Housing units built between 1990 and 2000 GCHA200G Housing units built between 1970 and 1989 GCHA300G Housing units built between 1950 and 1969 GCHA400G Housing units built between before 1950 Area GCAREA00G Land area in square kilometers The Summary File 1 variable used to allocate census block group data to census blocks is shown in the righthand column: Population GCPOP300G Total population GCP2500G Population age 25 and older GCPVP00G Total population GCHH300G Number of households Income GCSEVP00G Total population GCPOV00G Total population GCLOWI00G Total population GCAHHI00G Number of households Education GCEDU00G Population age 25 and older Housing GCHU300G Number of housing units GCOCC300G Occupied housing units GCHUNV00G Number of occupied housing units GCHA100G Number of housing units GCHA200G Number of housing units GCHA300G Number of housing units GCHA400G Number of housing units For more details, see the spreadsheet included in the archive (SF3_Variable_documentation.xls). DATA RESTRICTIONS These data are for noncommercial use only. No third party distribution of all, or parts, of the electronic files is authorized. CITATION Center for International Earth Science Information Network (CIESIN), Columbia University. 2005. U.S. Population Grids (Summary File 3), 2000: Alabama, Louisiana, and Mississippi (alpha version). Palisades, NY: Socioeconomic Data and Applications Center, CIESIN, Columbia University. http://sedac.ciesin.columbia.edu/hurricane2005.html DATA ERRORS, CORRECTIONS AND QUALITY ASSESSMENT CIESIN follows procedures designed to ensure that data disseminated by CIESIN are of reasonable quality. If, despite these procedures, users encounter apparent errors or misstatements in the data, please contact SEDAC User Services at 845/365-8920 or via e-mail at ciesin.info@ciesin.columbia.edu. Neither CIESIN nor NASA verifies or guarantees the accuracy, reliability, or completeness of any data provided. This version of the data is a preliminary "alpha" version designed for preliminary testing and review. Due to the pressing need for data posed by Hurricanes Katrina and Rita, we are making this dataset available for external distribution. Please provide us with feedback on any problems or errors with the data that you uncover. NO WARRANTY OR LIABILITY CIESIN provides this data without any warranty of any kind whatsoever, either express or implied. CIESIN shall not be liable for incidental, consequential, or special damages arising out of the use of any data provided by CIESIN. QUESTIONS If you have questions about these data, contact SEDAC User Services at 845/365-8920 or via e-mail at ciesin.info@ciesin.columbia.edu. ACKNOWLEDGEMENTS This work, including access to the data and technical assistance, is provided by CIESIN, with funding from the National Aeronautics and Space Administration under Contract NAS5-03117 for the Continued Operation of the Socioeconomic Data and Applications Center (SEDAC).