Big Redistricting News Out Of PA!

[politicallefty]

Interestingly as shown by Moun's district above, the 2010 numbers really encourage PA-17 to be Luzerne+Lackawanna+Monroe - the three counties are only a few hundred voters off of baseline. Such a district would be 51.7-44.6 Trump, compared to the current districts 54-43. It would have a Even PVI whereas the current district has a R+1. The thing really anchoring Pubs in the current PA-17 is Schuylkill, the one real remnant of the 2000 PA-17. The county was Tim Holden's base, and so it was grafted on to all the former Dem areas of PA-11.

The thing about PA is that the geography really favors the Pubs. Most fair maps can really only get 10/11 Obama districts out of a state Obama won by 10%. A 2012/2016 fair map of PA typically has:

-5 Solid Blue Districts: 4 in Philly Metro and one in Philly
-4 Marginal districts:  two in Metro, one in Lehigh valley, one in Northeast - my maps tend to have these all never leave a D+1/R+1 margin
-1 rarely competitive R seat somewhere with a R+5/6/7 PVI
-8 Safe Republican Seats across the state.

A fair map only really gives the Dems one seat, and pushes the four remaining swing seats closer to the center. The state favors the Pubs, and if this wasn't looking like a Democratic year, a fair map might not really change the state arithmetic.

I was digging through some of my old redistricting maps that I made prior to the 2012 election (so, based on Obama/McCain numbers) and I hadn't realized how badly Western PA has slipped away. Back then, Democrats would've been happy with an Erie-based district that took in the counties along the border with Ohio (which would've been a highly competitive R+1 district that Obama had won). The other district would've been a larger version of the old PA-20 (Greene, Fayette, Washington, and chunks of Beaver and Allegheny). It barely voted for McCain and I think that's only because McCain and Palin campaigned heavily in SWPA in the late days of 2008 campaign. Both of those would now be R+7 districts. Not impossible, but not even close to competitive. But that's really why the current PA-18 looks like it does, as opposed to being anchored in the corner (Westmoreland having already moved against Democrats federally).

Prior to 2010, Democrats controlled the PA delegation 12-7 and that's without PA-06 or PA-15 (although Democrats really had no business holding PA-10). The old PA-17 was really a Holden district, not a Democratic district. In that map, holding a majority of the delegation was contingent upon holding a majority of the marginal districts. We don't really know how relevant the Trump numbers are in some of these districts. For all we know, they could be as relevant as Obama's 2008 performance in states like Michigan and Wisconsin. In particular, I'm thinking about the reconstituted Lackawanna/Luzerne and Lehigh Valley districts. The former would've been considered a solid Dem district prior to 2016.

I think in any event, in a fair map, PA-07 will be gone for Republicans. There is absolutely no reason not to have Delco entirely contained within one district, creating a near-safe D+8 district. One thing I think makes things far more dangerous for Republicans in the new more competitive marginals is that incumbency is also mitigated, not to mention what it means if 2018 is a wave election with brand new districts.

Not to split hairs or anything, but I think there could be as many as three districts in your third category (R+5-7). Your point is still valid though. The geography of Pennsylvania is definitely tougher for Democrats now than it was several years ago. Even if Trump's numbers outside of SEPA inflate Republican performance, Western PA has been moving in their direction more than SEPA has for the Democrats (at least as far we can tell right now). To be honest, for all they hype, I was not at all impressed with Hillary's SEPA numbers. It does appear though, at the local level, that Trump's unpopularity is translating to Democratic gains. It remains to be seen if that will work it's way up to the state and federal level.

[politicallefty]

My Pennsylvania redistricting plan.

Apart from you did to Philly and excessive county splits, it's not too bad overall. PA-01 and PA-02 should both be contained within Philadelphia County. As for having two different districts pick up the remnants, I can see the merits to such a plan, but I'm not sure how others view that. Pulling PA-01 forces a counter-clockwise rotation that pushes a lot of PA-13 out of Philly and into Montco which in turn pushes PA-06 into Chester County and therefore parts of PA-07 out of Chester (as it entirely takes in Delco). I do like your PA-12 though. It's not something I see in Pennsylvania maps very often, but it's a very logical district.

[politicallefty]

For a plan with N districts, there should not be more than N-1 county chops without a clearly definable reason. In a state like PA with lots of well defined cities, towns and Philly wards (identified by the names of the vote districts in DRA) there is no reason other than trying for exact population equality to chop any of them. Doing so divides a community of interest (less so with some of the wards). There are enough of those county subdivisions that it should always be possible to get within a relatively small deviation, probably under 1000 and certainly less than 0.5%.

The five Philly area counties plus Berks and Lancaster are a near perfect fit for 7 CDs with 2010 data. There should be no more than 6 chops in those counties, and this plan does that (3 chops in Philly, 1 each in Montco, Delco, and Chester. I don't know if towns and wards were preserved whole though, but I presume some minor adjustments could be made to respect those lines.

The county splits out west are a different matter. I know ASV said he thought the communities of interest are more important, but I'm not how that applies there. The western boundary of Cambria and Somerset counties is a significant mountain ridge that is largely protected by state forests. It seems that this plan tries to use the next, lower ridge to the west as the line separating communities of interest, but that doesn't comport with the actually lifestyle patterns in that part of the state from my visits. Those county lines in this case do a pretty good job of marking the separation between regions.

I think that PA-01 is a violation of any fair and reasonable map. Philadelphia has the population for at least two districts. I think that should require, in any fair map, that the city/county should have two districts within its boundaries. That does mean an additional chop of Chester, however I believe the preceding criteria should take precedence. And furthermore, I think the other problem with SEPA in that map is that PA-13 takes in two non-contiguous parts of Philadelphia.

Like I said, I don't think it's an overall unreasonable map apart from what I mentioned above. It just needs some cleaning up in terms of county splits. I would work on it myself, but I don't want to start from scratch. To start, I would swap numbering between PA-11 and PA-17 and I would make the new PA-11 a Lackawanna/Luzerne/Monroe district.

[politicallefty]

There is a school of thought that says one redistricting principle should be: In any county greater than the population for a whole district there should be a number of districts completely within the county equal to the population of the county divided by the quota for one district, rounded down to the nearest whole number. In PA that would require 2 CDs in wholly in Philly, 1 wholly in Montco, and 1 wholly in Allegheny.

We debated the merits of this principle on threads on this board back in 2012-13. In the end the majority view here was that a count of the total number of chops was a more important principle than considering how the fragments of the chops nested within counties. I shared that view in part from my experience in the 2011 OH Redistricting Competition, which had nesting requirements for legislative districts and rules that created a preference for wholly-contained districts in the congressional plan. I thought it created unneeded skews to other measures of the plan.

I'm not sure I necessarily agree, but I admit I haven't fully explored the issue. I have always considered it a high priority when I've drawn maps. For PA, I have always followed the requirements you noted of that criteria. For OH, that would mean one district each entirely contained within each of Cuyahoga, Franklin, and Hamilton Counties. I don't really see a strong argument against having such a standard.

In this case, however, the two criteria are not in conflict (unless chopping a county an additional time violates certain criteria). In the map we're discussing, the districts basically move counter-clockwise. PA-01 moves out of Delco, eliminating the chop of that county. And ultimately, through a number of changes, PA-06 moves into Chester County, which adds a chop.

I do have one question about your criteria. Do non-contiguous chops from one district count as one or more (such as PA-13 in the map above)?

[politicallefty]

Here's the definitions worked out on the subject of chops (edited to reflect current use). Chops involving more than one fragment of a district are still just a chop. However, chops involving multiple fragments will typically have higher erosity, as each fragment counts separately for connections. The creates a small disincentive for fragmented chops, but that fragmentation might preserve towns or wards from additional chops.

Definition: Chop. A single chop is the division of a geographic unit between two districts. A second chop divides the unit between three districts. In general the number of chops is equal to the number of districts in that unit less one.

Definition: Chop size. In units with a single chop, the size of a chop is the population of the smaller district within the unit. For districts with more than one chop, chop sizes are measured in order from the smallest populated district in the unit up to but not including the district with the largest population in the unit.

Definition: Macrochop. A macrochop is one or more chops in a county that has a total size in excess of 5.0% of the quota. When a macrochop of a county occurs, the subunits of the county must be considered as if they were units as well. Note that macrochops may only apply to counties with a population of more than 10% of the quota, and must apply to counties with more than 105% of the quota.

Item 10: CHOP measures the integrity of geographic units in a plan. The CHOP score is the total of all county chops. In counties with a macrochop, chops of county subunits are added to the CHOP score, however VTDs that span county subdivisions do not increase the CHOP score.

Ugh, my first response died in a browser crash. I just have to say, for someone that places county integrity so high, I don't understand why you don't place the criteria I mentioned higher. If a county can support a certain number of districts within its boundaries, I think it should be required to do so. Philadelphia County should have two districts completely within its boundaries.

Thank you. My guess at PVI relying in part on the Toomey numbers which I think are more indicative of party strength going forward than the Trump coalition, is that PA-01, 02, 07, 13 and 14 are Dem bastions, PA-17 has a Dem PVI of about 2, PA-08 is a swing seat with a Pub PVI of maybe 1 and quite stable overall, PA-06 and PA-15 both have a Pub PVI of about 2 (with PA-06 trending Dem, and PA-15 fairly stable overall), and  the other 9 seats are Pub bastions. After the 2020 census, one of the Pub bastion seats (i.e. PA-05) will disappear.

I think SWPA could be drawn better. Attaching Butler County to the remainder of Allegheny seems like a Republican strategy. I think a more fair map would attach the remainder of Allegheny with Beaver County.