DOI: 10.7910/dvn/5lavkv
title: 2020 Census Redistricting Data (P.L. 94-171) Noisy Measurement File

description: The 2020 Census Redistricting Data (P.L. 94-171) Noisy Measurement File (NMF) is an intermediate output of the 2020 Census Disclosure Avoidance System (DAS) TopDown Algorithm (TDA) (as described in Abowd, J. et al [2022] &lt;a href="https://doi.org/10.1162/99608f92.529e3cb9"&gt;https://doi.org/10.1162/99608f92.529e3cb9&lt;/a&gt;, and implemented in &lt;a href="https://github.com/uscensusbureau/DAS_2020_Redistricting_Production_Code"&gt;https://github.com/uscensusbureau/DAS_2020_Redistricting_Production_Code&lt;/a&gt;). &lt;br/&gt;&lt;br/&gt;

The 2020 Redistricting NMF was an intermediate output of the DAS during the execution of the algorithm to produce the 2020 Census Redistricting Data (P.L. 94-171) Summary File. The NMFs are intermediate privacy-protected outputs of the DAS; they were generated using the &lt;a href="https://github.com/uscensusbureau/DAS_2020_Redistricting_Production_Code/blob/289ee463936a6f0efcf2e378abe410ec01d0e140/source/programs/engine/primitives.py#L183"&gt;Census Bureau's implementation&lt;/a&gt; of the Discrete Gaussian Mechanism (&lt;a href="https://arxiv.org/abs/2004.00010"&gt;https://arxiv.org/abs/2004.00010&lt;/a&gt;), calibrated to satisfy zero-Concentrated Differential Privacy (&lt;a href="https://arxiv.org/abs/1605.02065"&gt;https://arxiv.org/abs/1605.02065&lt;/a&gt;) with bounded neighbors (&lt;a href="https://dl.acm.org/doi/10.1145/1989323.1989345"&gt;https://dl.acm.org/doi/10.1145/1989323.1989345&lt;/a&gt;).&lt;br/&gt;&lt;br/&gt;

The NMF values, called "noisy measurements," are the output of applying the Discrete Gaussian Mechanism to counts from the 2020 Census Edited File (CEF). They are generally inconsistent with one another (for example, in a county composed of two tracts, the noisy measurement for the county's total population may not equal the sum of the noisy measurements of the two tracts' total population), and frequently negative (especially when the population being measured was small), but are integer-valued. The NMF was later post-processed as part of the DAS code to take the form of microdata and to satisfy various constraints. The NMF documented here contains both the noisy measurements themselves as well as the data needed to represent the DAS constraints; thus, the NMF could be used to reproduce the steps taken by the DAS code to produce microdata from the noisy measurements by applying the production &lt;a href="https://github.com/uscensusbureau/DAS_2020_Redistricting_Production_Code/blob/289ee463936a6f0efcf2e378abe410ec01d0e140/source/"&gt;code base&lt;/a&gt;.
description: &lt;br /&gt;The 2020 Census Redistricting Data (P.L. 94-171) Noisy Measurement 
File includes zero-Concentrated Differentially Private (zCDP) (Bun, M. and Steinke, T [2016]) noisy measurements, implemented via the discrete 
Gaussian mechanism. These are estimated counts of individuals and 
housing units included in the 2020 Census Edited File (CEF), 
which includes confidential data initially collected in the 2020 
Census of Population and Housing. The noisy measurements included 
in this file were subsequently post-processed by the 
TopDown Algorithm (TDA) to produce the 2020 
Census Redistricting Data (P.L. 94-171) Summary File.
description: &lt;br /&gt;The NMF provides estimates of counts of persons in the CEF by various characteristics and combinations of characteristics including 
their reported race and ethnicity, whether they were of voting age, 
whether they resided in a housing unit or one of 7 group 
quarters types, and their census block of residence after 
the addition of discrete Gaussian noise (with the scale 
parameter determined by the privacy-loss budget 
allocation for that particular query under zCDP). Noisy measurements 
of the counts of occupied and vacant housing units by 
census block are also included. Lastly, data on constraints—information into 
which no noise was infused by the Disclosure Avoidance System (DAS) and 
used by the TDA to post-process the noisy measurements into the 
2020 Census Redistricting Data (P.L. 94-171) Summary File —are provided.
description: Redistricting (PL), DHC