Lesson 3: Ways to Access Redistricting Data
In this lesson we will discuss the available methods you have to access redistricting data.
Once you understand the format of the data and each of these methods,
you can make a choice as to which of these methods meet your needs.
We will also briefly discuss the additional resources you may need or find helpful
to access these data.
Because there are many ways to access redistricting data and each of these ways has a different format and appeal,
let's discuss each one so that you can choose your learning path to move forward accessing these data.
The FTP is a great resource for those who want to perform in depth analysis and customize their analysis of datasets.
As for the format, when you select a state, you will be downloading all the files for
every level of geography available within that state.
The FTP is the only method to download the complete set of redistricting data files for each state.
Downloading from the FTP is a multi-step process
and it requires the use of a statistical analysis software to extract the data.
Pathway one will provide detailed instruction guiding you through how the download from the FTP step-by-step.
For this method of data access, you may need some additional resources,
because there are four large files for each state that you will download.
Downloading and storing the redistricting
data files from the FTP site will require computers with sufficient storage capacity.
You also need a software package that has a capability to extract this data from the FTP site
combining spatial and tabular data.
There are several options but are fast and Microsoft Access or a few.
If you would like to visualize your data on a map, you'll need tp download TIGER/line Shapefiles from census.gov .
And you can join the Shapefiles with the data in a program such as Maptitude, ARCGIS, or Tableau.
Even visualizations are an excellent choice for someone who wants an easy and
quick way to access the data and identify trends about a particular topic.
Each of the 2020 Census Redistricting Data Visualizations
offers their own unique features and topics,
such as population, race and ethnicity, voting age, and housing data.
Some of them allow you to
compare 2010 to 2020 Decennial Census statistics and some focus on just one topic different from
the FTP and data.census.gov.
When accessing data from a visualization you're only able to interact
with the data while using the visualization. Since in most cases you cannot download the data
on the other hand by visualizing the data on the map it becomes easier to spot trends.
Data.census.gov offers the most comprehensive method to access and use 2020 Census data.
It is a midway point between ease of use and the ability to download data. It gives you a customizable way
to view, map and access data one table at a time for all available geographies.
Data.census.gov is the Census Bureau's centralized place to get demographic, housing and economic data.
Data are offered in a tabular format but can also be viewed using a map.
It allows you to select a variety of geographies for all 2020 Census topics as individual tables.
So, this tool is maybe helpful
if you're looking for a particular topic for specific geographies from the available
redistricting data tables.
You can easily view data from a mobile phone as well as a desktop.
The Census API gives the public access to raw statistical data from various Census Bureau data
programs and enables developers to use our API to create and call customized datasets that feed into
web or mobile applications.
Many of our own Census Bureau tools and applications use our API.
Data.census.gov is a great example of this.
If you are interested in using Redistricting Data
to learn about how your community has changed overtime
between the 2010 and 2020 Decennial Censuses.
My colleague Alexandra Barker has some critical information for you
including do's and don'ts, useful tips, and resources to utilize for how to approach looking
for trends and changes while using these data. Let's check out what she has to say now.
Hi, I am Alexandra Barker. When trying to learn about how your community has changed overtime.
Is it possible to compare Redistricting Data from the 2020 Census with the 2010 Census? Yes,
You can make this comparison to assess trends and change in your area.
However, it is important to understand the do's and don'ts when making a comparison.
Tip #1 you can compare tables P1, P2,
P3, P4 and H1 from the 2010 Census and the 2020 Census.
These tables have the
same data fields and universe.
However, as part of the 2020 Census Redistricting data products
the Census Bureau released for the first table P5 for group quarters population.
in 2010, group quarters population by group quarters type was not released as part of the
redistricting products.
It was released with the main release of 2010 Census data
as table P42.
Therefore, you can compare table P5 from 2020 with table P42 from the 2010 Census.
Tip #2:
Be cautious about the geographic area that you select for your comparison.
It is critical that the boundaries for your area for the 2010 Census and the 2020 Census
are the same.
If the boundaries have changed from 2010 to 2020,
the data for these areas should not be compared.
Let me further explain this.
Every decade the Census Bureau redesigns the boundaries of blocks.
Therefore, a direct block comparison is not advised.
In order to provide
privacy within the data at the block level. the Census Bureau applies noise to the data.
So, let me show you an example of a block boundary redesign. Let’s check this map.
On the first map, you can see the block boundaries for the 2010 Census for an area in Massachusetts.
Pay attention to the boundaries of the blocks 1004 and 1008.
Now, look at the same area for the 2020 Census.
Not only the block numbers have changed but the two blocks from 2010 now form one block
number 1003.
And the boundary between the old blocks 1008 and 1003 have changed
with the one small part of the old block 1008, now being transferred to form the new block 1002.
Although it is true that the tabulation block universes are not directly comparable
from decade to decade, we included the 2010 to 2020 Census tabulation block.
crosswalk file in the geographic support products to help states and the public understand the
relationship between the 2010 and 2020 tabulation blocks.
So, this product makes some comparison
possible in support of redistricting.
So, click on the link above on this video or on the description of the video
to access the 2010 and 2020 Census Tabulation block crosswalk file.
Tip #3
If you want to compare that overtime for small areas, the census tract is a great geographic area.
However, you also must make sure
that the boundaries of the tracts that you are comparing remain the same between 2010 and 2020.
Between censuses, the Census Bureau reviews the boundaries of the tracts to make sure that its population
remains within the threshold of 1200 to 8000 people with an optimum size of approximately 4000 people.
Tracts are often split or merged from the regional tract boundaries.
but let me show you this on the map.
Let's say that between 2010 and 2020, the population grew
in census tract 1701
and the census tract was subsequently split into two tracts in 2020.
Each tract would get a suffix, 1701.01 and 1701.02.
Although the original tract was split,
the combined boundaries of the two new tracts it still makes up the original boundary of track 1701.
This is why tract boundaries are recommended for temporal analysis.
Tip #4
Another option that's relatively consistent from the decade to decade is counties.
Even when working with higher levels of geographies such as counties and states,
you need to make sure that their boundaries remained the same.
Although, it is more common to see annexation process take place at a city or town
it is possible but less common than annexation happens in a county or a state.
States and counties can submit annexations
and or boundary corrections for counties through the Annual Boundary Annexation survey.
But the frequency and number of updates to county boundaries from decades is small
compared to update submitted for other legal geographies such as incorporated places.
Tip #5
Since it is necessary to review the geography boundaries before making a comparison.
Let me take you to TIGERWeb Decennial for you to learn how to quickly determine if the boundaries
for your area of analysis have changed.
To learn, how to use Tigerweb Decennial,
watch Census Academies Data Gem 'Can I compare 2020 Census and 2010 Census Redistricting data?’
One of the best places to find resources and information on all five phases of the redistricting data program as their website.
There you can access the Redistricting Data files
technical documentation for how to access these data and more.
Alexandra will introduce you to several helpful resources on this webpage in Part 2.
Here's what you have learned in lesson 3.
You've learned your options for accessing redistricting data and then learned a little bit about each source
and if there were any
resources needed for downloading an analysis.
Alexandra then discussed the do's and don'ts
for comparison of 2010 and 2020 redistricting data.
Finally, we discussed the Redistricting Data Program website as being a best source for more information.
It's now time to pick one or more pathways. Which one will you choose?