2007-2009 ACS 3-year estimates
ACS 3-Year Estimates was available on our 2009, 2010, 2011, 2012 and 2013 versions but have been dropped for the 2010-2014 and all later data releases.
The 3-Year Estimates are only available for those geographies with a population of at least 20,000. That means you can run states or MSAs but if you try to run Counties you will only get 1,909 of the 3,220 counties to appear. The others simply don’t meet the population threshold and are suppressed (the USCB’s decision not ours).