ACS Data Users Group

I am trying to find or calculate population density for all Places in the US. I can find the population for these in a table like B01001 but I'm not sure if the land area is available in any form through one of the published tables.

Dear Cliff--

They do not put population density in the ACS, because they don't put in land area. Social Explorer has density because we use the data from the 2020 Census and how it is modified each year. They do modify places. Andy

Thanks Andy. Unfortunately, I suspected as much. Does anyone know if this data is available from the 2020 Census on data.census.gov?

Can you use the TIGER/Line shapefiles?

https://www2.census.gov/geo/tiger/TIGER2022/PLACE/

These include land and water areas in their attribute tables. Unfortunately there is no national shapefile for places, only state-level.

Yes it is. My suggestion, however, would make sure that the area of the places have not changed, because the place estimates and place ACS population counts are based upon redrawn places (if necessary). They put out every December new geographies. Tracts are the most complicated, because they do change a few tracts or did so in 2010, but quit by 2012. The areas and delineations of states, counties, and places are kept up to date. Why did I mention states, well one reason was the fight between NY and NJ over Liberty and Ellis Island. They don't give us density from the ACS, I think is a throwback to the issue of them not wanting anyone to use the ACS for population counts.

Glenn is right you could use the Tiger Line files. However, in the GEOheader file for 2020, there is a land and water area, that you can use to compute density. It needs to be converted to square miles, and then you need to decide what to do about the water. Given the fact that with Mermaid blocks in the 2020 Census some people are living underwater it becomes complicated. Boats can also be considered to be housing units. This obviously would only affect a few places.

Andy

Is there a single 2020 geoheader for all places, or would that material need to be downloaded on a state by state basis?

It comes with the 2020 Census. I don' know if he national PL94-171 File had a place summary level, but that would be where to look.

Final comment, if the area is updated you could use the newly released Tiger Line files for those that changed. They have a vintage as do the population estimates. Hope this is confusing enough:)

One further point, if you want to link business data from the business Census or the Zip or County Business Pattern data, the Economic Division uses a different set of geographies that they only update when they do a new economic Census. Also they use Zip codes, population division uses ZCTA.

They have a new "Frames" Project to harmonize some of this, but I would not hold my breath.

Andy

Andy and Glenn - Thanks for your help.

Does anyone know where to download the national PL94-171 File? I seem to be unable to find it through www2.census.gov.

Cliff, I don't know where you'd find this on the Bureau's site, but MCDC does have a compiled list of all US places (including land and water areas) from the 2020 PL94 data, in our data collection. The entry point is here:

https://mcdc.missouri.edu/cgi-bin/broker?_PROGRAM=utils.uex2dex.sas&path=/data/pl942020&dset=usplaces&view=0

It even has persons per (land) square mile.

The national redistricting file has places, which means one Geoheader file will have what you need. Areawater Arealand

Here is the doc: https://www2.census.gov/programs-surveys/decennial/2020/technical-documentation/complete-tech-docs/summary-file/2020Census_PL94_171Redistricting_NationalTechDoc.pdf

The data are here. I would recommend using the Legacy file format: https://www.census.gov/data/datasets/2020/dec/2020-census-redistricting-summary-file-dataset.html

Andrew, as far as I can see, these are all in state-level zip files, so Cliff would still need to download and unzip lots of individual files. Worse yet, they put each zip file in its own directory for no reason at all. Tedious!

If you're going to do that, you might as well grab the TIGER/Line shapefiles (can do all at once with a browser extension like DownThemAll, or script it), unzip them all, throw away everything but the DBF files, and combine and parse them with SAS or whatever.

Hi Cliff, I actually just did this calculation when creating this GIS feature layer of the new Demographic and Housing Characteristics (2020 Census DHC) for the three different place geographies (incorporated places, Census Designated places, and consolidated cities). The field in here is called P001_calc_pctPopDensity, People per sq. kilometer, and I calculated it this way: round(1,000,000 * (P0010001 / AREALAND), 1). If you have an ArcGIS Online account, you can sign in and export these tables to csv or whatever format you like.

Thank you Diana. Someone else provided me with the file I needed to calculate this data point but I will definitely take a look at your ArcGIS Online project.

Cliff,

We've got land and water areas (and populations, and therefore densities) for every state, county, metro, city, cosub, and zip code.
Shoot me an email and I'll hook you up.
Bert
bert@bestplaces.net

As an FYI you can use the R censusapi; package to download all the places (or County subdivision) mapping files for a state or county. You can pass a vector of FIPS codes to get the whole state. You can then pull out ALAND from the TIGERLINE datasets.

Thanks for the tip, David. We've also got the option of using GIS to total up the areas. One of our guys is a cartographic whiz and takes him only a couple of hours to do this sort of analysis.

Not to harp on this, but Density is a organic variable in Social Explorer, as such I was able to get Cliff Cook what he wanted in about 10 minutes. I finally decided to send it to him, because discussion how to do it was taking more time than it would take anyone with Social Explorer account to do it. Basically we set up and compute what many people are likely to want, so you do not have to.

True story. On the other hand, there is no pricing tab on Census Download pages. So there's that.

Generally there is pricing tab for either $ or time or both on people's efforts :).