5-year ACS vs 1-year ACS

I am planning to use a range of variables on a city-level, identified by the PUMA regions. It is important that each year is identified as I am looking at a certain policy change.

I understand that the 5-year sample is more accurate for small regions. Would it make sense to go with the 5-year data or are the respective years not exactly identified then.

Thank you!

The additional accuracy for smaller areas that the 5-year microdata sample provides is a result of aggregating observations from the five individual years of data collection since more observations, all else equal, will decrease standard errors. Using the 5-year file to get annual estimates (using MULTYEAR) eliminates this benefit. The 5-year files should be used to produce estimates that describe the five year period that they cover as a whole. Regarding the identification of CITY using PUMA, you should be aware that different cities are identified across vintages of PUMA (2000-2005; 2006-2011; 2012-2021; 2022-2031). The 5-year files that bridge these vintages (e.g. 2022 5-year) identify cities in each vintage separately. For example, a city that is identified in 2018-2021, but not in 2022, will have no observations in the 2022 portion of the 5-year file. Moreover, even when a city is identified across vintages, a change in the PUMA boundaries that affects the omission/commission error may also affect your results.

If your variables of interest are city-level aggregates rather than person-level microdata, then you might consider using IPUMS NHGIS to obtain your data. IPUMS NHGIS releases ACS data tables that summarize variables on small geographic levels such as metro areas and cities (without the use of PUMA as an intermediary step). The 1-year ACS summary data file provides tables for areas with at least 65,000 residents at several geographic levels, including the metropolitan/micropolitan area and place levels. The place level includes both legally defined cities and unincorporated places. For more information on getting started with IPUMS NHGIS, you can refer to the NHGIS FAQ page as well as the video tutorials in the user guide.