Im trying to find 2020 poptulation centroid data for GUAM and the CNMI.
Can anyone help guide me? ive been scouring the interwebs.
IPUMS NHGIS releases center of population coordinates from data provided by the Census Bureau. Data is available for Guam and the Northern Mariana Islands for 2000 (under centers of population by county), but not for either the 2010 or 2020 census. These are the only sources that we are aware of for this type of data. You may be able to estimate the center of population using the provided methodology documentation.
Thanks for the reply Ivan.
Question: Is there a way to create that data for 2020? I have a 2010 population centroid data sheet and shape file.
To follow the Census Bureau methodology, which Ivan linked to, you’d need block-level population data and geographic coordinates. We don’t have any data for Guam or the CNMI in IPUMS NHGIS. Based on the pages you linked to, it looks to me like the required block-level data for 2020 are now available somewhere on the Census website. Specifically, the “Demographic and Housing Characteristics File (DHC)” provides block-level statistics (and their coordinates), and those pages indicate that the 2020 DHC is now also available for the Island Areas.
As Jonathan notes, in order to create the data, you would need to follow the process outlined in the methodology report. The report notes that computation of the center of population in 2020 used census blocks where a point within each block was automatically determined by a computer program. The population counts and internal points are available for download on the TIGER/Line web interface. Technical documentation on the files is provided. The report continues, explaining that the latitude of the center of population was determined by multiplying the population of each unit of area by the latitude of its population center, then adding all these products and dividing this total by the total population. To calculate the longitude, the longitude of each of the points was multiplied by the cosine of the latitude of the point and by the population associated with the point. These products were added and then divided by the sum of the product of the cosine of the latitude and the population figure for each point. There may be GIS functions that will do this calculation for you, though I recommend confirming that they use the same method as specified in the technical documentation.