Abstract
In this paper, we apply techniques of ensemble analysis to understand the political baseline for Congressional representation in Colorado. We generate a large random sample of reasonable redistricting plans and determine the partisan balance of each district using returns from state-wide elections in 2018, and analyze the 2011/2012 enacted districts in this context. Colorado recently adopted a new framework for redistricting, creating an independent commission to draw district boundaries, prohibiting partisan bias and incumbency considerations, requiring that political boundaries (such as counties) be preserved as much as possible, and also requiring that mapmakers maximize the number of competitive districts. We investigate the relationships between partisan outcomes, number of counties which are split, and number of competitive districts in a plan. This paper also features two novel improvements in methodology—a more rigorous statistical framework for understanding necessary sample size, and a weighted-graph method for generating random plans which split approximately as few counties as acceptable human-drawn maps.
Similar content being viewed by others
Notes
We note that [12] also examines Colorado’s current legal definition of competitiveness, that is, “having a reasonable potential for the party affiliation of the district’s representative to change at least once between federal decennial censuses” [4] using probability, and finds that a literal reading of this law might be that “any district in which both parties have at least a 13% projected chance of winning might match the Colorado law, since (1–0.13)\(^5 \approx 0.5\)” [12].
References
Baker v. Carr (1962). 369 U.S. 186.
Rucho v. Common Cause (2019). 588 U.S.
An act to enforce the fifteenth amendment to the Constitution of the United States and for other purposes, August 6, 1965, Enrolled Acts and Resolutions of Congress, 1789-; General Records of the United States Government; Record Group 11; National Archives.
Congressional redistricting, November 6, 2018, Senate Concurrent Resolution 18-004, Amendment Y to Colorado Constitution.
Legislative redistricting, November 6, 2018, Senate Concurrent Resolution 18-005, Amendment Z to Colorado Constitution.
Barry, J. (2020). email communication, July 10.
US Census Bureau. (2010). 2010 census.
Chen, J., & Rodden, J. (2013). Unintentional Gerrymandering: Political geography and electoral bias in legislatures. Quarterly Journal of Political Science, 8(3), 239–269.
Chikina, M., Frieze, A., & Pegden, W. (2017). Assessing significance in a Markov chain without mixing. Proceedings of the National Academy of Sciences, 114(11), 2860–2864.
Cirincione, C., Darling, T. A., & O’Rourke, T. G. (2000). Assessing South Carolina’s 1990s congressional districting. Political Geography, 19, 189–211.
DeFord, D., Dhamankar, N., Duchin, M., Gupta, V., McPike, M., Schoenbach, G., & Sim, K.W. (2021). Implementing partisan symmetry: Problems and paradoxes. Political Analysis (to appear)
DeFord, D., Duchin, M. & Solomon, J. (2020). A Computational Approach to Measuring Vote Elasticity and Competitiveness. Statistics and Public Policy, 7(1), 69–86. https://doi.org/10.1080/2330443X.2020.1777915.
DeFord, D., Duchin, M., & Solomon, J. (2021). Recombination: A Family of Markov Chains for Redistricting. Harvard Data Science Review. https://doi.org/10.1162/99608f92.eb30390f
Diaconis, P. (2009). The Markov chain Monte Carlo revolution. Bulletin of the American Mathematical Society (N.S.), 46(2), 179–205.
Dimitrova, D. S., Kaishev, V. K., & Tan, S. (2020). Computing the Kolmogorov-Smirnov distribution when the underlying CDF is purely discrete, mixed, or continuous. Journal of Statistical Software, 95, 1–42.
Duchin, M., Gladkova, T., Henninger-Voss, E., Klingensmith, B., Newman, H., & Wheelen, H. (2018). Locating the Representational Baseline: Republicans in Massachusetts, arXiv e-prints, arXiv:1810.09051
Frank, J. (2019). Colorado hits a new milestone with unaffiliated voters and busts the myth about its even partisan split, Colorado Sun.
Herschlag, G., Kang, H. S., Luo, J., Graves, C. V., Bangia, S., Ravier, R., & Mattingly, J. C. (2020). Quantifying Gerrymandering in North Carolina. Statistics and Public Policy, 7, 30–38.
Hobbs, G. (2002). In re reapportionment of the Colorado general assembly. Colorado Supreme Court, 45, P.3d 1237.
Hoover, T. (2011). Judge rules in favor of Democratic map in Colorado redistricting, The Denver Post.
Hyatt, R. (2011). Moreno et al. v. Gessler, Denver District Court Case No. 11CV3461.
Liller, D. (2020). The impact of competitive congressional districts on compactness and political subdivision splits in Colorado, Master’s Thesis, submitted to the Department of Geography at University of Colorado Colorado Springs.
Liu, Y. Y., Tam Cho, W. K., & Wang, S. (2016). PEAR: A massively parallel evolutionary computation approach for political redistricting optimization and analysis. Swarm and Evolutionary Computation, 30, 78–92.
Loevy, R. D. (2011). Confessions of a Reapportionment Commissioner—2011. https://faculty1.coloradocollege.edu/~bloevy/confessions/ConfessionsBook.pdf. Accessed June 2020
Mattingly, J. C., & Vaughn, C. (2014). Redistricting and the Will of the People, arXiv e-prints, arXiv:1410.8796
Metric Geometry and Gerrymandering Group. (2018). Comparison of Districting Plans for the Virginia House of Delegates, Technical report, https://mggg.org/VA-report.pdf. Accessed May 2020
Najt, L., DeFord, D., & Solomon, J. (2019). Complexity and geometry of sampling connected graph partitions, arXiv e-prints, arXiv:1908.08881
National Conference of State Legislatures, Redistricting and the Supreme Court: The Most Significant Cases, technical report, 2019. https://www.ncsl.org/research/redistricting/redistricting-and-the-supreme-court-the-most-significant-cases.aspx. Accessed June 2019
Colorado Secretary of State, Election Results Archives: 2018 General Election precinct-level results in Excel format (2020). https://www.sos.state.co.us/pubs/elections/Results/archive2000.html
Smirnov, N. (1939). On the estimation of the discrepancy between empirical curves of distribution for two independent samples. Moscow University Mathematics Bulletin, 2(2), 3–14 (English).
Acknowledgements
We would like to thank the MGGG Redistricting Lab for introducing us to this area and for copious assistance; University of Nebraska graduate student Austin Eide for invaluable assistance in getting started; Todd Bleess of the Colorado State Demography Office for a great starting map; Geographers Dr. Rebecca Theobald and Dwayne Liller; student researchers Edgar Santos Vega, Jose Monge Castro, and Kadin Mangalik; and generous Colorado College GIS experts Matt Cooney and Francis Russell.
Funding
J. Clelland was partially supported by a Collaboration Grant for Mathematicians from the Simons Foundation. H. Colgate was supported by the Colorado College Summer Collaborative Research Experience. D. DeFord was partially supported by a Prof. Amar G. Bose Research Grant.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Clelland, J., Colgate, H., DeFord, D. et al. Colorado in context: Congressional redistricting and competing fairness criteria in Colorado. J Comput Soc Sc 5, 189–226 (2022). https://doi.org/10.1007/s42001-021-00119-7
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s42001-021-00119-7