The ALA Office for Intellectual Freedom (OIF) does not claim comprehensiveness in recording challenges. Research suggests that for each challenge reported there are as many as four or five which go unreported. In addition, OIF has only been collecting data about banned books since 1990, so we do not have any lists of frequently challenged books or authors before that date.
- List of 100 most frequently challenged books 1990-99
- List of 100 most frequently challenged books 2000-09
- List of 100 most frequently challenged books 2010-2019
OIF receives reports from libraries, schools, and the media on attempts to ban books and compiles this information into lists in order to inform the public about censorship in libraries and schools. The ALA condemns censorship and works to ensure free access to information. For more information on ALA's efforts to condemn censorship, please explore Banned Books Week: Celebrating Your Freedom to Read.