# Crosswalk Issue **URL:** \ **Category:** NHGIS\ **Created:** [April 8, 2022, 5:51am UTC](https://forum.ipums.org/t/crosswalk-issue/4596 "2022-04-08T05:51:40Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![JonathanSchroeder](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.ipums.org/jonathanschroeder/32/70_2.png) [@JonathanSchroeder](https://forum.ipums.org/u/JonathanSchroeder)\ **Post date:** [April 11, 2022, 8:22pm UTC](https://forum.ipums.org/t/crosswalk-issue/4596/2 "2022-04-11T20:22:56Z")
The relationship between 2000 and 2010 census tracts is complex and many-to-many, so there is often no single 2000 tract code corresponding to a 2010 tract. A 2010 tract may correspond to multiple 2000 tracts or only to a small part of a 2000 tract, etc. For this application, I would recommend instead that you obtain 2000 poverty data for [2000 block group parts](https://www.nhgis.org/geographic-crosswalks#finding-bgp-data) and allocate those data to 2010 tracts using the [corresponding crosswalks](https://www.nhgis.org/geographic-crosswalks#download-from-block-group-parts). Then you could have 2000 poverty rates for 2010 tracts, corresponding directly to the 2010 tract codes in the LIHTC data. Your plan to use 2005-2009 data poses a special challenge because the 2009 5-Year ACS Summary File provides data for 2000 block groups but not for 2000 block group parts, and NHGIS doesn’t supply a crosswalk for 2000 block groups. Also, according to [ACS documentation](https://www.census.gov/programs-surveys/acs/technical-documentation/table-and-geography-changes/2009/geography-changes.html#par_textimage_2), “in 19 counties from 8 different states, many of the census tracts and block groups used to tabulate and present the 2005-2009 ACS 5-year estimates are either those submitted to the Census Bureau for the 2010 Census, or a preliminary version of 2010 Census definitions.” As a result, even if you [used NHGIS block crosswalks](https://forum.ipums.org/t/can-i-use-nhgis-crosswalk-for-block-group-level-data/2750) to interpolate the 2005-2009 block group data to 2010 tracts, there’d be additional complications in these 19 counties. If it’s possible for you to use 2006-2010 ACS instead of 2005-2009 data, that would simplify matters, enabling you to match data directly to the 2010 FIPS codes in the LIHTC data. --- _[View the full topic](https://forum.ipums.org/t/crosswalk-issue/4596)._