Calculating median age for a group of US census blocks?

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

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

This is correct on the second question, at least for more recent censuses.  On the first question, imagine a block where the ages of three individuals are 60, 50, and 40, and another one where the ages are 20, 20, and 20.  Using your approach you would have 50 * 3 = 150 for the first block, and 20*3 = 60 for the second block.  The median of 60 and 150 is 105.  Even dividing that by three you get 35, which is not the correct median age (30).

-----Original Message-----
From: R-sig-Geo <r-sig-geo-bounces at r-project.org> On Behalf Of Josiah Parry
Sent: Monday, August 7, 2023 2:38 PM
To: Kevin Zembower <kevin at zembower.org>
Cc: r-sig-geo at r-project.org
Subject: Re: [R-sig-Geo] Calculating median age for a group of US census blocks?

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 at 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

	[[alternative HTML version deleted]]

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 at r-project.org <mailto:r-sig-geo at 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

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 at r-project.org <mailto:r-sig-geo at 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

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 at r-project.org <mailto:r-sig-geo at 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 at r-project.org <mailto:r-sig-geo at r-project.org>

    <mailto:r-sig-geo at r-project.org <mailto:r-sig-geo at 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
     >
     >? ? ?_______________________________________________
     >? ? ?R-sig-Geo mailing list
     > R-sig-Geo at r-project.org <mailto:R-sig-Geo at r-project.org>

    <mailto:R-sig-Geo at r-project.org <mailto:R-sig-Geo at r-project.org>>

     > https://stat.ethz.ch/mailman/listinfo/r-sig-geo

    <https://stat.ethz.ch/mailman/listinfo/r-sig-geo>

     >? ? ?<https://stat.ethz.ch/mailman/listinfo/r-sig-geo

    <https://stat.ethz.ch/mailman/listinfo/r-sig-geo>>

     >