Each set of crosswalk files links the RSEI grid cell geography to a different US decennial census year. There is one crosswalk for each area and decennial Census year (1990, 2000, 2010). Crosswalk files are named by area (Alaska, Con(terminous) US, etc.).

The last three fields in each file contain percent values that can be used to adjust the block or cell contents when performing the crosswalk. PCT_B_C and PCT_C_B are area-weighted and can be used for metrics that do not involve population, such as concentration and toxicity-weighted concentration. PCT_PC_B is population weighted, and can be used to crosswalk fields that involve population, like score and pop.

Note that the "PCT_CP_B" field is not available for the territories (VI, PR, GU, AS, MP). The Northern Mariana Islands are in the Guam file and the Virgin Islands are in the Puerto Rico file. There are no crosswalks for Puerto Rico, the Virgin Islands, Mariana Islands, Guam, or American Samoa for 1990.  For these areas, RSEI uses 2000 block boundaries and scales each cell’s population by the overall ratio of 1990/2000 population for each area.