This study focuses on understanding the variability in levels of unit response rates for the American Community Survey (ACS). Analysis is limited to data collection for housing units, and explores a broad set of geographic levels such as national, state, and sub-state level geography, such as county. While response rates have been strong at national and state levels, we have not looked to see whether the strong rates hold for the full set of areas for which we publish data. In this report, we will study the sub-state level geography response rates to ensure the rates are at an acceptable level. For this evaluation, 1-year response rates were calculated over the individual years from 2005 to 2007, the first three years of full implementation of the ACS. Three-year response rates were calculated for the full 2005-2007 period. The 1-year response rates were computed for all geographic areas with 65,000 or more people, while the 3-year response rates were calculated for all geographic areas with 20,000 to 65,000 people. Results suggest that response rates for the ACS are very strong for the first three years that the ACS was in full implementation. The national response rate was around 97 percent for these years. The response rates at sub-state levels of geography are also strong. For areas wit h 65,000 or more people (1-year areas), there are no instances when the response rate was below 80 percent, and over 90 percent of these areas had response rates of 95 percent or higher. The distributions and ranges of response rates for the sub-state levels of geography are similar in nature to that of the higher-level geographies. Mean response rates across the sub-state levels of geography are in the 97 to 98 percent range and only a few in these areas fall below 90 percent. Areas that will only receive 3-year estimates and not 1-year estimates (areas with populations of 20,000 to 65,000) also showed strong response rates, with no areas falling below 84 percent. Therefore, the ACS overall attains high response rates for all published geographies for 2005 to 2007.