Lab: Redistricting after the Census
Insure that you update both the program and help file, and are running
2017.4.5 or newer. Also, go to Options, Menus tab, and select "show labs".
Open Annapolis redistricting (File, GIS
Labs, Annapolis Redistricting). If you wanted to use
create the dataset in MICRODEM.
After reading the column by Foer, the leadership of the Historic Annapolis
Hispanic Alliance has asked you to investigate whether it would be possible to
create a ward in the city which will be majority Hispanic. Even if that is not
possible, they project that the Hispanic population will continue to rise (it
went from 6.7% to 15.6% between 2000 and 2010), will continue to be concentrated
in the same neighborhoods, and they might be able to elect someone even if the numbers would not currently indicate they would have the votes.
They would like you to create the most hispanic-friendly district possible in
the city, subject to the following constraints:
- The population must be within 5% of the target, which is
1/8th of the city population. This was the largest
deviation at the start of the 2010 redistricting; because of uneven growth,
the current ward 4 was 15.9% too populous, while ward 8 was 12.5%
- The ward must be contiguous; you cannot simple cherry pick
the most populous Hispanic blocks. It does not have to
be compact, but can emulate some of the
congressional districts you can see online.
- After you create the best possible Hispanic ward, they would
like to see if it possible to retain two majority Black
- Discussion of whether the highest population densities in
the city (> 10000/km²) are
segregated by race and Hispanic ethnicity. You should have
a map and some numbers to back this up. To do this filter
the blocks by population, and then look at the totals for each
- Discussion of whether the lowest population densities in the
city (< 1000/km²) are segregated by
race and Hispanic ethnicity. You should have a map and
some numbers to back this up. Do not include the water and
commercial blocks which have no population.
- Word document showing the final Ward maps, and a discussion
about how hard it is to come up with the desired ward makeups.
- KMZ file showing your Ward map. This will probably be
best if you export the final map rather than the database.
- Use File, GIS Labs,
Annapolis Redistricting. This will
open several datasets:
- TIGER map with the edges/lines, and the
census blocks overlaid. If this does not appear
- A database with all the blocks in the city of Annapolis, with their
populations after the 2010 census.
- A redistricting form with the districts and their current populations.
- Randomize the districts before you start, with the clear, Randomize
Districts command. To keep the districts contiguous, start with either
vertical or horizontal bands. Insure that you have 8 districts.
- We will try to get 8 districts for the city council.
You have the following constraints:
- Each must be within 5% of the target population (“one person, one
- We would like two district to have a
majority black population.
- Districts must be contiguous and not be
- Population estimates only include those who reported
themselves as solely White, Black, or Asian. This is a
slight simplification, but the multiple race categories make
analysis very complex. Hispanic is totally separate from
- Population estimates include only the total population, and
do not use the separate data tables with those over 18 who are
the only ones eligible to vote.
- Data uses the original data from the US Census Bureau, and
does not consider the state readjustment of incarcerated
prisoners who are returned to their homes instead of being
included in the districts with the state prisons.
- Does not consider that some people counted may be illegal
aliens and not eligible to vote, or that the age distributions
of some groups may have higher percentages of children who
Things to note:
- The population blocks include schools,
government buildings, shopping centers, and other commercial blocks.
These will be clear on the maps.
- There are some big blocks, like the football stadium, which have a few
houses in one corner, and get an artificially low population density.
Redistricting Form detailed
Last revision 5/29/2015