[R-sig-Geo] Calculating median age for a group of US census blocks?

Kevin Zembower kev|n @end|ng |rom zembower@org
Tue Aug 8 21:31:50 CEST 2023


Dexter, Thanks so much for your reply. I wasn't aware of the two sources 
you cite, and I'll be sure to include them in my work.

The open Baltimore website, at 
https://data.baltimorecity.gov/datasets/neighborhood-1/explore, has 
statistics for my neighborhood, Radnor-Winston 
(https://radnorwinston.org).The Baltimore Neighborhood Indicators 
Alliance at https://bniajfi.org/vital_signs/ lumps us into North 
Baltimore/Guilford/Homeland, which, as I'm sure you're aware, contains 
many homes (mansions!) with very different characteristics than the 
people of Radnor-Winston.

Thanks, again, for your help and expertise. I learned a lot from your note.

-Kevin

On 8/7/23 15:43, Dexter Locke wrote:
> Hi Kevin and all,
> 
> Given the binned data, you could count the number of people per age 
> class for those 10 blocks. You can then express that in a number of 
> different ways, like percent under 25 years old, or by calculating the 
> dependency ratio 
> <https://www.who.int/data/gho/indicator-metadata-registry/imr-details/1119#:~:text=Definition%3A,a%20specific%20point%20in%20time.>.
> 
> I do think it is feasible to calculate an estimated mean from the counts 
> within groups representing ranges. See, for example, here: 
> https://stackoverflow.com/questions/18887382/how-to-calculate-the-median-on-grouped-dataset <https://stackoverflow.com/questions/18887382/how-to-calculate-the-median-on-grouped-dataset>
> 
> Since you are working in Baltimore, you may consider looking at The 
> Baltimore Neighborhood Indicators Alliance 
> https://bniajfi.org/vital_signs/ <https://bniajfi.org/vital_signs/>. 
> They provide useful data on a range of issues (transportation, crime, 
> education, environment etc.) including summaries from Census-derived 
> demographics. What you are seeking may already exist. BNIA creates 
> neighborhoods or "community statistical areas" (n=55) based on 
> aggregates of Census data.
> 
> Although not pertaining to age, Baltimore City Planning has paid Census 
> in the past to aggregate from individual-level Census data to the more 
> colloquially-used definitions of Baltimore shown here (n = 273): 
> https://data.baltimorecity.gov/datasets/neighborhood-1/explore?location=39.284832%2C-76.620516%2C12.91 <https://data.baltimorecity.gov/datasets/neighborhood-1/explore?location=39.284832%2C-76.620516%2C12.91>
> 
> Best, Dexter
> https://dexterlocke.com/ <https://dexterlocke.com/>
> 
> 
> 
> 
> 
> On Mon, Aug 7, 2023 at 3:02 PM Kevin Zembower via R-sig-Geo 
> <r-sig-geo using r-project.org <mailto:r-sig-geo using r-project.org>> wrote:
> 
>     Josiah, thanks for your reply.
> 
>     Regarding my objective, I'm trying to compile census statistics for the
>     blocks that make up the neighborhood where I live. It consists of ten
>     census blocks, of which I selected three for simplicity in my example.
>     The census block-group which contains these ten blocks also contains
>     some blocks which are outside of my neighborhood and shouldn't be
>     counted or included.
> 
>     Since I won't be able to calculate the median age from the age and
>     count
>     data, and since the individual data doesn't seem to be available, is it
>     your thought that I can't produce a valid median age for a group of
>     census blocks?
> 
>     Thanks so much for your advice.
> 
>     -Kevin
> 
>     On 8/7/23 14:38, Josiah Parry wrote:
>      > Hey Kevin, I don't think you're going to be able to get
>     individual level
>      > data from the US Census Bureau. The closest you may be able to
>     get is
>      > the current population survey (CPS) which I believe is also
>     available
>      > via tidycensus. Regarding your first question, I'm not sure I follow
>      > what your objective is with it. I would use a geography of census
>     block
>      > groups as the measure of median for census block groups.
>     Otherwise it is
>      > unclear how you are defining what a "group of blocks" is.
>      >
>      > On Mon, Aug 7, 2023 at 2:34 PM Kevin Zembower via R-sig-Geo
>      > <r-sig-geo using r-project.org <mailto:r-sig-geo using r-project.org>
>     <mailto:r-sig-geo using r-project.org <mailto:r-sig-geo using r-project.org>>>
>     wrote:
>      >
>      >     Hello, all,
>      >
>      >     I'd like to obtain the median age for a population in a
>     specific group
>      >     of US Decennial census blocks. Here's an example of the problem:
>      >
>      >     ## Example of calculating median age of population in census
>     blocks.
>      >     library(tidyverse)
>      >     library(tidycensus)
>      >
>      >     counts <- get_decennial(
>      >           geography = "block",
>      >           state = "MD",
>      >           county = "Baltimore city",
>      >           table = "P1",
>      >           year = 2020,
>      >           sumfile = "dhc") %>%
>      >           mutate(NAME = NULL) %>%
>      >           filter(substr(GEOID, 6, 11) == "271101" &
>      >                  substr(GEOID, 12, 15) %in% c(3000, 3001, 3002)
>      >                  )
>      >
>      >     ages <- get_decennial(
>      >           geography = "block",
>      >           state = "MD",
>      >           county = "Baltimore city",
>      >           table = "P13",
>      >           year = 2020,
>      >           sumfile = "dhc") %>%
>      >           mutate(NAME = NULL) %>%
>      >           filter(substr(GEOID, 6, 11) == "271101" &
>      >                  substr(GEOID, 12, 15) %in% c(3000, 3001, 3002)
>      >                  )
>      >
>      >     I have two questions:
>      >
>      >     1. Is it mathematically valid to multiply the population of a
>     block by
>      >     the median age of that block (in other words, assign the
>     median age to
>      >     each member of a block), then calculate the median of those
>     numbers for
>      >     a group of blocks?
>      >
>      >     2. Is raw data on the ages of individuals available anywhere
>     else in
>      >     the
>      >     census data? I can find tables such as P12, that breaks down the
>      >     population by age ranges or bins, but can't find specific data of
>      >     counts
>      >     per age in years.
>      >
>      >     Thanks for your advice and help.
>      >
>      >     -Kevin
>      >
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