Users of the 2018-2022 ACS 5-Year PUMS file in the Microdata Access Tool (MDAT) may have noticed that PUMAs are no longer available among the list of geographies. But why is that? In this tutorial we’ll help you understand the concept of Dual Vintage PUMAs in the ACS 5-Year PUMS, why these changes temporarily occurred, and highlight some things to keep in mind before using PUMAs from the 2022 ACS 5-Year PUMS in our Microdata Access Tool.