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Steven Ruggles Profile picture
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3 Jul, 8 tweets, 3 min read
Here is a screenshot from yesterday's Census Bureau Webinar on new specifications for the 2020 census. The table shows the crazy inconsistencies in the block-level data, comparing the version they adopted April 28 with the new version just announced./1
The demonstration data released in April was terrible, as we and others explained.
We were expecting the new version to be more accurate than the previous one, but for blocks it turned out even worse./2
users.pop.umn.edu/~ruggles/Artic…
The Census Bureau is deliberately introducing the errors because they claim it is necessary to protect privacy. I dispute that claim in this working paper. /3
assets.ipums.org/_files/mpc/wp2…
Under the new specifications, the number of blocks with no people but with occupied housing units almost doubled, to 149,000. There are zero blocks like that in the real data./2
The number of blocks with no people but with occupied housing units almost doubled, to 149,000. There are zero blocks like that in the real data./3
As I mentioned yesterday, the Lord-of-the-Flies blocks with all children and no adults went from 91,000 to 164,000 in the new "production" version of the data. No such blocks exist in the real data./4
This graph from the Webinar shows the mean error in the population census blocks under the old system and the new one. /5
The previous version got the population of Liberty Island wrong by a factor of 24. In the new data, it is likely that the population of small blocks is off by at least an order of magnitude. Data of that quality is not worth producing./end

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More from @HistDem

Steven Ruggles Profile picture
1 Jul
It has now become clear that the 2020 Census will not provide block-level statistics usable for planning or research./1
Newly-published data reveal that the Census Bureau has increased the "noise" added to the data at the block level, compared with the demonstration data released in April./2
census.gov/programs-surve…
That data was already highly problematic, but the new data the Census Bureau plans to release is even worse. For example, in 303,000 blocks there are fewer people than occupied housing units./3
Read 10 tweets
Steven Ruggles Profile picture
9 Jun
Back in December 2018, Mark Hansen wrote an article on differential privacy in the NYT. To explain how the Census protected identities in 2010, he cited the case of the only two residents of Liberty Island in New York harbor, who oversee the national monument./1
Liberty Island is considered a block by the Census Bureau, even though it only has two residents. The actual residents of the island were a married couple, who were interviewed by Hanson, aged 59 and 49, who both identified as white./2
To protect their identities, the Census Bureau “swapped” the couple with a different couple residing nearby, a 63 year-old-man and a 58-year old woman who identified themselves as Asian./3
Read 12 tweets
Steven Ruggles Profile picture
8 Jun
Somehow I missed this subtweet. @frankmcsherry finds it "mystifying" that "(some) demographers" (i.e. me) have "contempt for the the privacy of their subjects." In his blog quotes, he screenshots my tweets and characterizes them as "just embarrassing."/1
In my tweets, I was objecting to @john_abowd's characterization of a 45% match rate between his so-called database reconstruction and the actual data on four characteristics as "highly accurate."
Since then, I have demonstrated that the supposed reconstruction had a match rate only slightly better than one would expect by chance.
assets.ipums.org/_files/mpc/wp2…
Read 9 tweets
Steven Ruggles Profile picture
3 Jun
There has been so much happening on the Census Bureau’s disclosure avoidance plans that it can be hard to follow. Here’s a quick guide to key developments over the past three months. /1 Image
Back on March 10, the State of Alabama filed a lawsuit objecting to the use of differential privacy in the census, arguing that the infusion of deliberate errors into the data is unconstitutional./2
The lawsuit also argues that the decision to implement differential privacy and to delay the redistricting numbers is “arbitrary and capricious” in violation of the Administrative Procedure Act./3
Read 21 tweets
Steven Ruggles Profile picture
2 Jun
The Census Bureau has conducted a new analysis that purports to show that swapping is ineffective for the prevention of reidentification attacks. /1
www2.census.gov/about/partners…
The new analysis completely misses the point, and actually provides a useful demonstration of the gross misrepresentation of the Census Bureau’s “Database Reconstruction Experiment.” /2
The Census Bureau claimed that without swapping, they could “putatively re-identify” 44.60 of the population. /3
Read 12 tweets
Steven Ruggles Profile picture
21 May
/1. Yesterday at the ACS Data Users Conference, the Census Bureau described its plans to replace the American Community Survey (ACS) microdata with “fully synthetic” data over the next three years.
/2. Details of the methodology have not been disclosed, but the idea is to develop models describing the interrelationships of all the variables in the ACS, and then construct a simulated population consistent with those models.
/3. Such modeled data captures relationships between variables only if they have been intentionally included in the model. Accordingly, synthetic data are poorly suited to studying unanticipated relationships, which impedes new discovery.
Read 30 tweets

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