[Music] Hi, I am Alexandra Barker.
When trying to learn about how your community has changed over time, 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 dos and don’ts when making a comparison. So,
in this data gem I will go over some tips about how to compare redistricting data from the 2020
Census with the 2010 Census. So come along with me. Tip number one, you can compare tables P1,
P2, P3, P4 and H1 from the 2 010 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 release for the first timetable 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 number two, 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 addition, 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 1 block number 1003 and the boundary between the old blocks
1008 and 1003 have changed with 1 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 the caged 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 to 2020 Census tabulation block crosswalk file.
Tip number 3, if you want to compare data over time 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 4,000 people.
Tracts are often split or merged from the original 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 a split the
combined boundaries of the two new tracts is still makes up the original boundary of
tract 1701. This is why tract boundaries are recommended for temporal analysis.
Tip number four another option that's relatively consistent from the cage decade is
Counties. Even when working with higher levels of geographies such as counties and states
you need to make sure that their boundaries remain the same.
Although it is more common to see an annexation process take place at a city or town it is
possible but less common that 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 to decade is small
compared to updates submitted for other legal geographies. Such as incorporated places.
Tip number five, 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 you can visit TIGERweb
by clicking on the link above in this video or in the description of the video.
Once you load the application you can start zooming into the area of your interest.
Let's go back to Massachusetts. We will be looking for the same tracts that we looked
at earlier in this data gem. Next, let's add the tract boundaries and labels to this map
go to the left side menu and check the box for census tracts and blocks.
Expand the plus sign just make sure that you have the boundary selected.
You can use the bar to make your boundary transparent.
Let's continue to zoom in to find tract 1701.01. Here it is, let's get closer.
This view includes the boundaries and labels for block groups and blocks.
Let's remove the boundaries and labels for blocks and block groups to have a clear view
of the boundary of the tracts. Move to the left side menu. Use the plus sign to expand
for census tracts and blocks and uncheck census block groups and census blocks.
Now we can see the boundaries for the tracts for the year 2020. Let's select a new vintage so
we can look at the boundaries for 2010. Click on Census 2010 and uncheck the Census block boundary.
You can see that this tract was a single tract 1701 but if you change again to the view for 2020
you see this tract was split in 2. This is a great resource
for you to determine if the boundaries of your geographies have changed between Censuses.
I hope you found these tips helpful. If you would like to learn more about 2020 Census
redistricting data visit census.gov/academy and don't forget to subscribe. Thank you.