Study on Congressional District Compactness
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Miles
MilesC56
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« on: November 12, 2013, 03:55:00 PM »

The software mapping company Azavea put out this report on CD compactness.


These are the districts it finds to be least compact (in descending order):

NC-12
FL-05
MD-03
OH-09
TX-35
NC-04
LA-02
FL-22
MD-06
NY-10

Top ten states with the lowest average compactness among their districts:

MD
NC
LA
WV
VA
HI
NH
IL
PA
RI

Anyway, it was neat to read through!
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publicunofficial
angryGreatness
Junior Chimp
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« Reply #1 on: November 12, 2013, 06:08:31 PM »

I'm curious how Hawaii ended up on the least compact list.

The districts are 1) Honolulu 2) Everything else.
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Smid
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« Reply #2 on: November 12, 2013, 06:15:45 PM »

I'm curious how Hawaii ended up on the least compact list.

The districts are 1) Honolulu 2) Everything else.

Perhaps they counted the coastlines around each of the major islands as part of the electoral boundaries or something?
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RedSLC
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« Reply #3 on: November 12, 2013, 07:54:14 PM »

I'm curious how Hawaii ended up on the least compact list.

The districts are 1) Honolulu 2) Everything else.

HI-2 probably skews the state as a whole, because it's a chain of islands. If that's what it is, then HI would probably have to be a special case to account for this.
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jimrtex
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« Reply #4 on: November 12, 2013, 11:27:40 PM »

I'm curious how Hawaii ended up on the least compact list.

The districts are 1) Honolulu 2) Everything else.

Perhaps they counted the coastlines around each of the major islands as part of the electoral boundaries or something?
Hawaii does very poor on the measurements that use perimeter, which might indicated crinkly or convoluted boundaries, so it might just be the coastline around all the islands.  If Pearl Harbor is excluded, HI-1 could also be very convoluted given its small size.  It is conceivable that they connect all the islands with long threads so that HI-2 is contiguous.



In that case, the perimeter is extreme, it would be like NC-12 but worse.
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muon2
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« Reply #5 on: November 12, 2013, 11:33:56 PM »

The listed compactness measures have inherent biases with certain types of districts. Measures that compare perimeter to area do poorly with wiggly natural boundaries like coastlines and rivers. Measures that compare district area to the area of a regular shape like a circle do better with natural features but fail with intrinsic shapes like the WV panhandles. They also don't catch districts that are gerrymandered with a cut out area since they can mimic natural boundary shapes.
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ElectionsGuy
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« Reply #6 on: November 13, 2013, 12:46:35 AM »

The software mapping company Azavea put out this report on CD compactness.


These are the districts it finds to be least compact (in descending order):

NC-12
FL-05
MD-03
OH-09
TX-35
NC-04
LA-02
FL-22
MD-06
NY-10

Top ten states with the lowest average compactness among their districts:

MD
NC
LA
WV
VA
HI
NH
IL
PA
RI

Anyway, it was neat to read through!

Interesting, not a surprise though. Almost all those states and districts that you mentioned have massive gerrymanders.
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Antonio the Sixth
Antonio V
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« Reply #7 on: November 13, 2013, 03:04:34 AM »

This is why "compactness" as a mathematical concept is not the right way to measure the quality of redistricting.
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jimrtex
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« Reply #8 on: November 19, 2013, 09:55:45 PM »

The listed compactness measures have inherent biases with certain types of districts. Measures that compare perimeter to area do poorly with wiggly natural boundaries like coastlines and rivers. Measures that compare district area to the area of a regular shape like a circle do better with natural features but fail with intrinsic shapes like the WV panhandles. They also don't catch districts that are gerrymandered with a cut out area since they can mimic natural boundary shapes.

District   State   Area   Perimeter   Polsby-Popper   Schwartzberg   Convex Hull   Reock   Polsby-Popper Z Score   Schwartzberg Z-Score   Convex Hull Z-Score   Reock Z-Score   Average Z-Score   Polsby-Popper Rank   Schwartzberg Rank   Convex Hull Rank   Reock Rank

HI-1 Area 541.1 Perimeter 256.6
Polsby-Popper    0.103 -1.124 61 (raw value, Z-score, and rank).
Schwartzberg 0.321 -0.705 61 (raw value, Z-score, and rank)
Convex Hull 0.609 -1.124 98 (raw value, Z-score, and rank)
Reock 0.279 -0.705 84  (raw value, Z-score, and rank)
Average Z-score -0.914

HI-2 Area 16040.5 Perimeter 1723
Polsby-Popper    0.068 -1.361 21 (raw value, Z-score, and rank).
Schwartzberg 0.261 -1.613 21 (raw value, Z-score, and rank)
Convex Hull 0.836 1.131 381 (raw value, Z-score, and rank)
Reock 0.458 0.759 326  (raw value, Z-score, and rank)
Average Z-score -0.271

Since both districts fare badly under the perimeter-based measure, it must be due to the coastline, though HI-1 is also going to be hurt for following mountain ridges - and possibly Pearl Harbor. 

HI-2 does very well on Reock and Convex Hull.  Area outside the state but within the convex hull or circumscribing circle must be excluded from the calculation.

Are there alternatives to using a Z-score, I suspect that most of the measures are not very linear?

Trivia question:

Which are the districts which are most compact?

Hint 1: One district is best under two different measurements.
Hint 2: At-large districts are not included, so AK, MT,WY, ND, SD, DE, and VT are excluded.
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Smid
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« Reply #9 on: November 19, 2013, 10:03:33 PM »

Trivia question:

Which are the districts which are most compact?

Hint 1: One district is best under two different measurements.
Hint 2: At-large districts are not included, so AK, MT,WY, ND, SD, DE, and VT are excluded.

Nevada's 1st seems to be fairly compact?
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jimrtex
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« Reply #10 on: November 19, 2013, 11:38:08 PM »

Trivia question:

Which are the districts which are most compact?

Hint 1: One district is best under two different measurements.
Hint 2: At-large districts are not included, so AK, MT,WY, ND, SD, DE, and VT are excluded.

Nevada's 1st seems to be fairly compact?
Yes.  NV-1 the northern district benefits from having borders with CA, OR, ID, and UT as well as a pretty straight southern border, and is not overly wide EW to NS.

NV-1 is first in Polsby-Popper which is based on comparing the area of the district with that of a circle that has a circumference equal to the perimeter of the district.

NV-1 is also first under Schwartzberg which is based on comparing the circumference of a circle that has same area as the district with the perimeter of the district.

The ranking of all districts is the same under both measurements.
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jimrtex
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« Reply #11 on: November 21, 2013, 11:27:18 PM »

Trivia question:

Which are the districts which are most compact?

Hint 1: One district is best under two different measurements.
Hint 2: At-large districts are not included, so AK, MT,WY, ND, SD, DE, and VT are excluded.

Nevada's 1st seems to be fairly compact?
Yes.  NV-1 the northern district benefits from having borders with CA, OR, ID, and UT as well as a pretty straight southern border, and is not overly wide EW to NS.

NV-1 is first in Polsby-Popper which is based on comparing the area of the district with that of a circle that has a circumference equal to the perimeter of the district.

NV-1 is also first under Schwartzberg which is based on comparing the circumference of a circle that has same area as the district with the perimeter of the district.

The ranking of all districts is the same under both measurements.

Hint 3: The district that is most compact under Convex Hull is being challenged as a racial gerrymander.

Hint 4: Think of a fruit that would be compact under the Roeck test.
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