From the summary:
On the basis of GAO’s nationwide generalizable survey of local election jurisdictions, GAO estimates that 78 percent (from 74 to 83 percent) of jurisdictions did not collect data that would allow them to calculate wait times, primarily because wait times have not been an issue, and most jurisdictions did not have long wait times on Election Day 2012. Specifically, GAO estimates that 78 percent (from 73 to 83 percent) of local jurisdictions nationwide had no polling places with wait times officials considered to be too long and 22 percent (from 17 to 27 percent) had wait times that officials considered too long at a few or more polling places on Election Day 2012. Jurisdiction officials had varying views on the length of time that would be considered too long—for example, some officials considered 10 minutes too long, while others considered 30 minutes too long. Because there is no comprehensive set of data on wait times across jurisdictions nationwide, GAO relied on election officials in the jurisdictions it surveyed to estimate wait times based on their perspectives and any data or information they collected on voter wait times.
Multiple factors affected voter wait times on Election Day 2012, and their impacts varied across jurisdictions. Specifically, GAO’s survey of local election jurisdictions, review of wait time literature, and interviews with election officials and researchers identified nine common factors that affected wait times….