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

[Dexter Locke]

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

Since you are working in Baltimore, you may consider looking at The
Baltimore Neighborhood Indicators Alliance 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

Best, Dexter
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> 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>> 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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> >
>
>
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