ACS 5-year estimates Census Tract Boundaries

For ACS 5-year estimates that straddle 2010 (2007-2011 to 2009-2014), or all census tract estimates from the 2010 Census Tract boundaries?  My guess would be that this would be the case starting with the 2006-2010 ACS estimates, but I just wanted to confirm. 

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  • Yes, sort of. Each 5-year ACS estimate uses the boundaries from the last year of its range (eg. 2007-2011 uses 2011). Tract boundaries from 2010 to 2019 are similar. There are a few certain specific tracts in upstate New York, Arizona, and Los Angeles whose boundaries or numbers changed in 2011 and 2012. Those changed tracts will not match up with data from non-matching years, so you'll see null data on your map. The most fastidious thing to do would be to use the correct boundary for each ACS estimate. That may be overkill, so next best would be to use 2011 for 2007-2011, and 2012 for years beyond that. You could use 2012 boundaries for all your data, and have a few nulls in 2011, or 2011 boundaries and have a few nulls in 2012-2014; depending what you're doing and where you're looking at, these changes might not be of concern to you.

    Also just to note that other boundaries, like CBSAs, places, county subdivisions, and a few counties, have more changes throughout the decade.

  • Hi, Bernie.  Thanks for the information.  I had assumed that Census Tract boundaries were stable between Census years, but it appears as though this is not the case.   We are just focusing on New York City, so we may be okay.  Will have to check if there were any changes to NYC Census Tract boundaries

  • The changes in New York State are all in Madison and Oneida counties (except combining some water tracts off Staten Island), AND they all happened in 2011, so I don't think you have to worry about changes in NYC. Here's info on that: https://www.census.gov/programs-surveys/acs/technical-documentation/table-and-geography-changes/2011/geography-changes.html

    And though it's not relevant to you, for completeness, here's info on the Arizona and California tracts changed in 2012: https://www.census.gov/programs-surveys/acs/technical-documentation/table-and-geography-changes/2012/geography-changes.html

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