Administrative
Report
N.2., File # 21-3058 Meeting Date: 11/9/2021
To: MAYOR AND CITY COUNCIL
From: BRANDY FORBES, COMMUNITY DEVELOPMENT DIRECTOR
TITLE
DISCUSSION AND POSSIBLE ACTION ON 2020 CENSUS AND DEMOGRAPHIC DATA AND CITY
COUNCIL REDISTRICTING REQUIREMENTS
EXECUTIVE SUMMARY
Section 7.1 of the City Charter requires the City Council to modify its Council District boundaries (if necessary) within nine months of receiving the decennial census data. The City received the data used for redistricting purposes on August 16, 2021, and therefore is required to adopt any necessary new district boundaries by May 16, 2022.
The Charter requires each district to be as nearly equal in population as practicable, in compliance with State and Federal Law. However, the 2020 Census population distribution includes a new mathematical algorithm called “differential privacy” that is intended to protect data and presumably preserve accuracy. In Redondo Beach this is manifesting as a major population shift, yet technically does not accurately reflect the location of those counted.
This item provides an opportunity for the City Council to begin discussing the 2020 Census data, how to account for the City’s population changes and the “differential privacy” algorithm, and provide direction on how to begin modifying the Council District boundaries.
BACKGROUND
The US Census Bureau released the data from the 2020 Census on August 16, 2021. Section 7.1 of the City Charter requires the City Council to modify its Council District boundaries (if necessary) within nine months of receiving the decennial census data. Therefore, the City is required to adopt any necessary new district boundaries by May 16, 2022. The Charter requires each district to be as nearly equal in population as practicable, in compliance with State and Federal Law.
Based on the 2010 Census, the City’s population was 66,748. Per the 2020 Census, the City population is now 71,576. In order to find a target number that equally represents the five council districts, the new population number divided by the five Council Districts results in a target number of 14,315 people per district (the target number when evaluating the 2010 Census was 13,350).
New to this year’s census is a process called “disclosure avoidance procedures” that were put in place to protect the confidentiality of the 2020 Census Redistricting Data. Per the US Census Bureau’s explanation (see attached Protecting the Confidentiality of the 2020 Census Redistricting Data document), historically, the Bureau has enhanced and strengthened how they protect the
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Data document), historically, the Bureau has enhanced and strengthened how they protect the confidentiality of the information they collect when individuals respond to surveys and censuses.
They note that by law they must ensure that they do not release information that could identify a person’s information in the statistics that they publish. The Census Bureau has recognized that with today’s technology, it is easier to take the information they release and reconstruct it or pair it with information gathered from other sources (commercial data brokers) to match datasets and identify people and their information within a set of data. Thus, they have implemented a “disclosure avoidance mechanism” to protect against these attacks.
The 2020 Census population distribution includes a new mathematical algorithm to provide the “differential privacy”. Although the intent is to both protect data and preserve accuracy, this framework is manifesting as a major population shift in Redondo Beach, yet technically does not reflect the location of those counted. This is demonstrated in the Census Blocks maps for 2010 and 2020 below.
Although there was some slight shifting of blocks from the 2010 Census to the 2020 Census (such as the waterfront areas), generally that information and trend carries over from one census to another.
However, with the mathematical algorithm, there is one census block that the data says increased from 162 in population in 2010 to 1,716 in population in 2020 (see red area on Census Blocks 2020 map). Yet this is a single-family residential zone and there was only one additional dwelling unit in that census block (increased from 62 housing units in 2010 to 63 housing units in 2020). Therefore, the algorithm that calibrates for redistricting data while protecting the privacy of data has skewed the additional population by adding a significant amount of the City’s total increase in population into this one census block rather than more appropriately distributing it throughout a larger area or the municipality as a whole.
N.2., File # 21-3058 Meeting Date: 11/9/2021
The 2020 Census reports exact counts for the following (these exact counts are referred to as “invariants”):
· The total population at the state level.
· The number and type of occupied group quarters facilities at the block level. · The number of housing units, whether occupied or not, at the block level.
Unfortunately, the population at anything less than the state level is calculated using the mathematical algorithm to provide differential privacy. The algorithm shows that the total population increase for the City from 2010 to 2020 is 4,828. However, the per block data reflects that almost 1/3 of that city-wide population increase from 2010 to 2020 is located in one single block in an R-1 zone (which only increased by a single housing unit over the 10-year period).
While there is no specific legal requirement indicating how much deviation in population is acceptable, a five percent deviation from the target number has historically been considered within acceptable limits in Redondo Beach. The 2010 distribution that was approved included the following distribution of population by Council District:
Table 1. 2010 District Population Distribution
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Utilizing the skewed 2020 population per block information that the Census Bureau published and using the current Council District boundaries, the Council Districts would need to be significantly revised--mainly to account for the skewed data representing the stated 1,554 population increase in the one referenced block in District 3. The following table represents that:
Table 2. 2010 and 2020 Population Based on Population by Block Distributed by Current District
City staff discussed the concern regarding the skewed data with Census Bureau representatives immediately after receiving the data and having prepared an initial breakdown of population by district. It was clear that at least the one census block had major data issues. The guidance the Census Bureau provided for addressing the published data anomaly, is to use the next larger
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Census Bureau provided for addressing the published data anomaly, is to use the next larger categorical area as the basis. The census block level is the lowest or smallest categorical level of geography. The next level is the census block group. However, with such a major misrepresentation in the one census block, it would still be skewed at the census block group level. This is represented in Table 2 where 82% of the additional population for District 3 is within that one skewed census block. At the time, the representative from the Census Bureau did not inform City staff of any procedures for requesting corrections or otherwise contesting the data.
On October 8, 2021 the Census Bureau posted information for corrections requests of this nature on their website. After reviewing the data more thoroughly to determine the issue with the algorithm and researching the options for requesting corrections, on November 2, 2021, City staff officially submitted a request for a correction of this skewed data. Per the US Census Bureau Correction Procedures, the Census Bureau will respond in writing within 60 days of receiving the complaint. That doesn’t ensure that the Census Bureau will have completed their review of the correction request in that timeframe, but will provide an expected review completion date in that response.
Staff is exploring other potential methodologies for more equitable distribution of the population by Council District. Since the “number of housing units at the block level” is an invariant, staff is considering how that statistic might be utilized. Another possibility is to determine a city-wide population per census block average to propose an amendment to the map. These potential methodologies can be further developed and considered if the Census Bureau does not make corrections to the data.
As noted previously, the City Charter requires the City Council to modify its Council District boundaries (if necessary) within nine months of receiving the decennial census data. The City received the data used for redistricting on August 16, 2021, and therefore is required to adopt any necessary new district boundaries by May 16, 2022. The Charter requires each district to be as nearly equal in population as practicable, in compliance with State and Federal Law. City staff are seeking direction from the City Council on how to consider distribution of population by block to determine what modifications to Council District boundaries may be needed.
COORDINATION
The Community Development Department Planning Division and the Public Works Department Engineering Division have coordinated the preparation of this administrative report. Staff have also communicated with the Census Bureau.
FISCAL IMPACT
The costs for developing recommendations on redistricting and reporting census and demographic data are included in the Community Development Department and Public Works Department’s portion of the adopted annual budget and included in the departments’ work programs.
APPROVED BY:
Joe Hoefgen, City Manager
ATTACHMENTS
Protecting the Confidentiality of the 2020 Census Redistricting Data provided by the US Census Bureau dated August 2021
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Census Blocks 2010 Redondo Beach Map
Census Blocks 2020 Redondo Beach Map
US Census Bureau Disclosure Avoidance Modernization Information website link:
<https://www.census.gov/programs-surveys/decennial-census/decade/2020/planningmanagement/process/disclosure-avoidance.html>