preserve county and municipality boundaries as much as possible (1)
Interpretation of requirements
We enforce a maximum population deviation of 0.5%.
We apply the standard algorithmic county constraint.
Data Sources
Data for Maine comes from the Voting and Election Science Team for 2016, 2018, and 2020. It is retabulated to 2020 Census tracts, as 2020 Census VTDs do not cover the majority of Maine's geography.
Pre-processing Notes
Islands tracts were connected to the nearest tract within the same district.
Simulation Notes
We sample 5,000 districting plans for Maine, across 4 independent runs of the SMC algorithm.
We use the standard county constraint.
We weaken the compactness parameter to 0.8 due to the relatively small state size and total number of tracts to encourage more diversity in the sample.
Validation
SMC: 5,000 sampled plans of 2 districts on 288 units
`adapt_k_thresh`=0.985 • `seq_alpha`=0.5
`est_label_mult`=1 • `pop_temper`=0
Plan diversity 80% range: 0.08 to 0.61
x WARNING: Low plan diversity
R-hat values for summary statistics:
pop_overlap total_vap plan_dev comp_edge comp_polsby pop_white pop_black
1.0016304 1.0006552 1.0011907 1.0007446 1.0013620 1.0028100 1.0016165
pop_hisp pop_aian pop_asian pop_nhpi pop_other pop_two vap_white
1.0019402 0.9997223 1.0001822 1.0002458 1.0011645 1.0022978 1.0022428
vap_black vap_hisp vap_aian vap_asian vap_nhpi vap_other vap_two
1.0012229 1.0014702 0.9997750 0.9999535 1.0007415 1.0017581 1.0010225
pre_16_dem_cli pre_16_rep_tru pre_20_dem_bid pre_20_rep_tru uss_18_dem_rin uss_18_rep_bra uss_20_dem_gid
1.0011891 1.0007762 1.0009348 1.0008138 1.0001335 1.0019796 1.0008980
uss_20_rep_col gov_18_dem_mil gov_18_rep_moo adv_16 adv_18 adv_20 arv_16
1.0036252 1.0023539 1.0056620 1.0011891 1.0017261 1.0009263 1.0007762
arv_18 arv_20 muni_splits ndv nrv ndshare e_dvs
1.0045683 1.0020944 1.0000876 1.0012118 1.0024344 1.0010895 1.0009055
pr_dem e_dem egap
1.0000605 1.0024182 1.0024065
Sampling diagnostics for SMC run 1 of 4 (1,250 samples)
Eff. samples (%) Acc. rate Log wgt. sd Max. unique Est. k
Split 1 1,160 (92.8%) 7.0% 0.4 801 (101%) 4
Resample 561 (44.9%) NA% 0.4 1,005 (127%) NA
Sampling diagnostics for SMC run 2 of 4 (1,250 samples)
Eff. samples (%) Acc. rate Log wgt. sd Max. unique Est. k
Split 1 1,180 (94.4%) 5.7% 0.39 775 ( 98%) 5
Resample 822 (65.8%) NA% 0.39 1,040 (132%) NA
Sampling diagnostics for SMC run 3 of 4 (1,250 samples)
Eff. samples (%) Acc. rate Log wgt. sd Max. unique Est. k
Split 1 1,168 (93.4%) 5.5% 0.39 797 (101%) 5
Resample 689 (55.1%) NA% 0.39 1,015 (128%) NA
Sampling diagnostics for SMC run 4 of 4 (1,250 samples)
Eff. samples (%) Acc. rate Log wgt. sd Max. unique Est. k
Split 1 1,178 (94.2%) 5.8% 0.38 795 (101%) 5
Resample 806 (64.5%) NA% 0.38 1,030 (130%) NA
• Watch out for low effective samples, very low acceptance rates (less than 1%), large std. devs. of the log
weights (more than 3 or so), and low numbers of unique plans. R-hat values for summary statistics should be
between 1 and 1.05.
• Low diversity: Check for potential bottlenecks. Increase the number of samples. Examine the diversity plot
with `hist(plans_diversity(plans), breaks=24)`. Consider weakening or removing constraints, or increasing
the population tolerance. If the accpetance rate drops quickly in the final splits, try increasing
`pop_temper` by 0.01.
Redistricting requirements
In Maine, following Title 21-A, Chapter 15, Section 1206, districts must:
Interpretation of requirements
We enforce a maximum population deviation of 0.5%. We apply the standard algorithmic county constraint.
Data Sources
Data for Maine comes from the Voting and Election Science Team for 2016, 2018, and 2020. It is retabulated to 2020 Census tracts, as 2020 Census VTDs do not cover the majority of Maine's geography.
Pre-processing Notes
Islands tracts were connected to the nearest tract within the same district.
Simulation Notes
We sample 5,000 districting plans for Maine, across 4 independent runs of the SMC algorithm. We use the standard county constraint. We weaken the compactness parameter to 0.8 due to the relatively small state size and total number of tracts to encourage more diversity in the sample.
Validation
Checklist
TODOlines from the template code have been removedenforce_style()to format my coderedist_mapandredist_plansobjects, and summary statistics) have been editedNotes: Low diversity due to having only two districts. Surprised that every plan is splitting one county.
@CoryMcCartan