Difference between poverty measure in ACS 2011 five-year estimates versus 2012 five-year estimates?

I am trying to conduct a time-series analysis on county-level poverty for 1990, 2000, and 2007-2011 and 2015-2019. However, even when I select the 2011 five-year estimates, I am directed toward 2012 five-year estimates in the time-series options. Given that the year 2011 is included in both sets of five-year estimates, I am not sure how or why the poverty measure would be different. Could someone please explain?

Thank you!

Currently, with few exceptions, NHGIS time series include ACS data only from the 2008-2012 and 2015-2019 5-year periods. We plan to extend the time series to include all 5-year periods, but there’s not a timeline set for that yet. Until then, you can still get the 2007-2011 5-year data via NHGIS “source tables.”

To understand why 2011 5-year estimates differ from 2012 5-year estimates, I recommend reading a little more on what 5-year estimates represent. One good resource is this opening chapter from the ACS Handbook for Data Users.

In short, “5-year estimates represent data collected over a period of 60 months.” The 2011 5-year estimates describe characteristics for the full 60-month span from January 2007 through December 2011. These differ from the 2012 5-year estimates because they include the 12 months of 2007 and exclude the 12 months of 2012.

Thank you!