CRS report via FAS – State Voter Identification Requirements: Analysis, Legal Issues, and Policy Considerations, Eric A. Fischer, Senior Specialist in Science and Technology; R. Sam Garrett, Specialist in American National Government; L. Paige Whitaker, Legislative Attorney. October 21, 2016.

“About 60% of U.S. voters live in the 32 states that require a voter at a polling place to produce an identification document (ID) before casting a ballot. Among those states, 19 permit voters without ID to cast a ballot through alternative means, such as signing an affidavit; 13 strictly enforce the ID requirement. The other 18 states and the District of Columbia have a range of non document requirements instead. Over the last two decades, the number of states requiring voter IDs has tripled. The stringency of those requirements is controversial. States vary substantially in the range of IDs accepted, the information they must contain, and the ease with which a voter can procure an ID. Although all states requiring voter ID accept a local driver’s license, no two states have the same overall requirements. Among states with voter ID laws, 18 require photographic identification (photo ID), while 14permit a non photo ID . In addition, eight states require ID for voters casting absentee or mail-in ballots…”