a period when single issue sales fell. Even 2017, which saw both trades and single issue sales fall compared to 2016, trades were down 9.38%, compared to single issues dropping 10.4%". In 2019, Bleeding Cool emphasized, "in recent years, collected issues/trade paperbacks are more popular and profitable than monthly comic book periodicals. As single issue sales have consistently plummeted, trade paperbacks and graphic novels have filled in the gaps. From 2013 to 2018, graphic novels were the highest-selling format for comic books". According to industry reports, "the massive shift to graphic novels as the preferred format for comics continued in 2019 bringing sales in the book channel above the comic store channel in North America for the first time in the history of the medium" and that "the sales of graphic novels were growing faster in the book trade than in comics shops". Trade paperbacks and graphic novels are the preferred format for circulating library collections, since these collections are created to be read, and not to be retained as collector's items or as investments. Attempts to catalogue and circulate single-issue comics can pose difficult problems and the durability of the trade paperback format is an important consideration for longevity and collection development in public and school libraries. Trade paperbacks "are also the primary culprit in people's confusion of the lexicon, since 'TPBs make up 95% of what many librarians refer to as graphic novels'". See also Graphic novel Limited series Omnibus edition Tankōbon References Comics formats Comics terminology