Can I use NHGIS Crosswalk for Block Group Level Data?

I have been able to use the NHGIS crosswalk to interpolate Census 2000 block level data to Census 2010 block boundaries. How can I do the same with Census 2000 block group level data? I would like to use source variables that are only available at the block group level.



The NHGIS block-to-block crosswalks can help for this application, but they are not by themselves sufficient. Some additional modeling is required.

Let’s say for example that you want to interpolate 2000 foreign-born population (FBP) from 2000 block groups to 2010 block groups. A general workflow is:

  1. Dis-aggregate FBP from 2000 block groups to 2000 blocks

  2. Use the NHGIS block-to-block crosswalk to interpolate FBP estimates from 2000 blocks to 2010 blocks

  3. Sum the 2010-block-level estimates of 2000 FBP within each 2010 block group

Steps 2 and 3 are relatively straightforward. For Step 1, you’d have to estimate how 2000 block-group populations are distributed among 2000 blocks.

In this example, it would make sense to allocate FBP among blocks in proportion to the block population. I.e., you’d assume that the distribution of FBP among blocks within each block group is proportionally the same as the population distribution. So if one block contains 3% of the the block group’s population, you’d assign that block 3% of the block group’s FBP.

For other statistics, it would be better to use other block characteristics to guide the disaggregation. E.g., to disaggregate aggregate household income, it would make sense to use block-level household counts. To disaggregate population 25 years and over with a bachelor’s degree, it would make sense to use block-level counts of population 25 years and over. Etc.

If you need to interpolate many block-group statistics, you may also want to start by generating your own block-group-to-block-group crosswalk. E.g., for each intersection between a 2000 block group and 2010 block group, use 2000 block data and the NHGIS block-to-block crosswalk to estimate the proportion of the 2000 block group’s population that lies in the 2010 block group. Then you could re-use the smaller BG-to-BG crosswalk to interpolate each statistic you need to interpolate. If you want to use different guide variables for different statistics (e.g., households instead of population), then you’d have to add each of those proportions to your crosswalk.

NHGIS has plans to construct crosswalks like these, and to generate standardized time series of block-group source data, using the same techniques I described above. However, it may be a year or more before these products are available.

That makes sense!



Have there been any updates or progress with constructing these block-group crosswalks?

Yes, we’re getting very close! We expect to release this new batch of crosswalks within 2-3 weeks, hopefully by mid-August at the latest.

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Awesome, will be eagerly looking out for the release. Thank you for this resource!

Just wondering if there was a status update on the release of these crosswalks? Thank you!

I’m aiming for later this week (Thursday or Friday) barring any surprises.

Crosswalks for block group parts are now available!


@JonathanSchroeder Assume I want to use the crosswalk to go from 2000 block groups to 2010 block groups and that my variable of interest is only available at the 2000 block groups level. How can we go from 2000 block group parts to 2000 block groups? Is there another crosswalk for that? Thank you!

Could you clarify what you’re looking for and why?

First, you say, “my variable of interest is only available at the 2000 block groups level”, but to my knowledge, there are no 2000 census datasets that provide data for block groups and not also for block group parts. What is your source? If it’s the 2000 census, I think you should be able to get the same data for block group parts.

Second, you ask, “How can we go from 2000 block group parts to 2000 block groups?” This implies that you have data for 2000 block group parts and you want to allocate it to 2000 block groups. Is that right? If so, rather than starting with data for block group parts, you could instead get the same data at the block group level because 2000 census datasets that provide data for block group parts also provide data for block groups.

Lastly, if it is the case that you need a crosswalk we haven’t created, my first response in this forum post provides some general guidance about how to use block-to-block crosswalks to generate crosswalks from any other source units.

Hi Jonathan,

Thank you so much for this detailed explanation. I’ve been following some of your posts on moving from block groups w/ 2000 Census boundaries to tracts w/ 2010 Census boundaries. I am trying to harmonize 2009 ACS data (2000 Census boundaries, albeit with geography issues) to 2010 Census Tracts (similar to this poster). I know 2009 ACS is not available at the block group part level, and I couldn’t find a crosswalk on NHGIS Crosswalks page that would allow for 2000 block group → 2010 tract. Do you know if NHGIS plans to create this crosswalk (somehow negotiating the issues with the 19 counties, etc.)? Or is this a situation where I need to generate my own crosswalk (as you explain based on populations/weights) in the above post? Thank you so much for fielding all these questions. And my apologies in advance if I missed something on this forum or NHGIS’s website.

Angela, thanks for pointing out this gap in our crosswalk collection. We’ve had no plans to create crosswalks from 2000 block groups because, as noted in my reply in this post from last week, I know of no 2000 datasets that provide BG data and not BG part data. But you’re right that the 2005-2009 ACS data use (mostly) 2000 BGs and not BG parts. I’ve added a new item to our to-do list to construct crosswalks from “2009 block groups”, which would account for the oddities in the 19 counties. But I can’t say if or when we’ll get to that, so yes, I think the best strategy for now is the one you describe, generating your own crosswalk.

Hi Jonathan, thank you so much for this thorough response. I’ll keep an eye out for any updates to the crosswalks. Appreciate all your great work!