Copyrightability of Charts, Tables, and Graphs | U-M Library
Excellent analysis of the case history and interpretation of copyright law. The quick answer is that because data itself can't be copyrighted, charts and graphs that just represent that data also can't be copyrighted. Infographics are an exception because they can demonstrate creativity.
Charts, graphs, and tables are not subject to copyright protection because they do not meet the first requirement for copyright protection, that is, they are not “original works of authorship,” under the definitions in the Act.
