Colorado’s 2021 redistricting of congressional and legislative districts is well underway even in the face of unusual obstacles. 

Preliminary staff-drawn maps of congressional districts were released last week by Colorado’s Independent Congressional Redistricting Commission, and initial state Senate and House district maps drawn by the Independent Legislative Redistricting Commission’s non-partisan staff will be issued Tuesday. 

Samuel Greenidge

Then, both commissions will be hitting the road starting July 9 to hear feedback on these maps at public hearings across the state.

The greatest obstacle thus far in the process has been the lack of 2020 census data. Colorado’s Independent Redistricting Commissions are required by law to use these numbers to ensure that every district has nearly equal population.

Unfortunately, the release of these numbers has been delayed from April 1 to Aug. 16. This delay threatened to derail the 2022 election calendar, force a rushed job on election maps that will be used for a decade, or both. 

In order to prevent this, the commissioners voted unanimously to use a preliminary population dataset until the final census numbers are released. The full dataset is available here, and in the interest of transparency, I’d like to share how it was constructed.

The preliminary dataset is the result of extensive collaboration between our staff and the Colorado State Demography Office, two strictly non-partisan entities. It is a preliminary dataset that is only being used for our preliminary maps. The final maps will incorporate the feedback we get on these preliminary maps, but they will be drawn using the final census numbers exactly as the law requires.

So far, the Census Bureau has given us exactly one number: 5,773,714. That is Colorado’s total 2020 population, so that’s our starting point. The Colorado State Demography Office maintains population estimates for every municipality and county, so we’ve adjusted those estimates to match the census number exactly. 

We’ve distributed the population within each county and municipality in accordance with the number of houses and apartments in each census block recorded in the Census Bureau’s Master Address File. Vacancy rates and group quarters numbers from the 2010 Census were used to avoid overcounting areas with vacation homes or undercounting prisons, universities, and military bases. 

This gives us a population distribution that is reasonably close to reality with a total population that is exactly the same as the final 2020 census number.

But redistricting is about more than just population. The Voting Rights Act of 1965 requires that no electoral district be drawn which disenfranchises a racial, ethnic, or linguistic minority, so we need demographic information too. 

Fortunately, the Census Bureau collects data that can fill this need. In addition to the decennial census, they perform the American Community Survey, an annual survey of a statistically rigorous sample of the population which measures demographic data for each census block group. In Colorado this translates to groups of 1,500 people on average. Even the smallest districts drawn by the state commissions, state House districts, will contain around 89,000 people. 

So while this demographic data is not as detailed as we expect the 2020 census data to be, it is statistically sound and provides enough information for our preliminary maps.

The final shortcoming of our preliminary dataset is a technical one. The smallest geographic units of census data are census blocks. In urban areas they’re roughly equivalent to a city block, in more rural regions they’re larger areas bounded by rivers, roads, and other clear boundaries. 

Out of necessity, our preliminary dataset is sorted into blocks from 2010. These blocks are fairly similar to the 2020 block geography, but many small uninhabited 2010 blocks (such as highway clovers) were combined with other blocks, and some larger populated blocks were split into smaller blocks. We think the differences will be manageable. 

Using these 2010 boundaries keeps the redistricting schedule on track, and our preliminary dataset compatible with industry standard software, so that the public can draw maps directly on our website.

If you have any questions or comments for the commissions you can submit them online, sign up to speak at one of our online meetings, or speak to us in person at one of our 39 public hearings. Thirty-two of these will be held in towns throughout Colorado in July and August, and one more will be held in each of the current congressional districts once we have the 2020 census numbers this fall. 

Ultimately these maps belong to every Coloradan, and we need your input to draw fair districts.

Samuel Greenidge, an unaffiliated member of the Colorado Independent Legislative Redistricting Commission and a student at the University of Colorado Boulder, has been a Colorado resident for 22 years, raised in Weld County.

The Colorado Sun is a nonpartisan news organization, and the opinions of columnists and editorial writers do not reflect the opinions of the newsroom. Read our ethics policy for more on The Sun’s opinion policy and submit columns, suggested writers and more to (Learn more about how to submit a column.)

Read more opinion. Follow Colorado Sun Opinion on Twitter, Instagram and Facebook.