Nancy Drew is a fictional character sleuth in an American mystery series created by publisher Edward Stratemeyer as the female counterpart to his Hardy Boys series. The character first appeared in 1930. The books are ghostwritten by a number of authors and published under the collective pseudonym Carolyn Keene. Over the decades, the character evolved in response to changes in US culture and tastes. The books were extensively revised and shortened, beginning in 1959, in part to lower printing costs with arguable success. In the revision process, the heroine's original character was changed to be less unruly and violent. In the 1980s, an older and more professional Nancy emerged in a new series, The Nancy Drew Files, that included romantic subplots for the sleuth. The original Nancy Drew Mystery Stories series started in 1930, and ended in 2003. Launched in 2004, the Girl Detective series features Nancy driving a hybrid electric vehicle and using a cell phone. In 2012, the Girl Detective series ended, and a new current series called Nancy Drew Diaries was launched in 2013. Illustrations of the character evolved over time to reflect contemporary styles. The character proves continuously popular worldwide: at least 80 million copies of the books have been sold, and the books have been translated into over 45 languages. Nancy Drew is featured in five films, two television shows, and a number of popular computer games; she also appears in a variety of merchandise sold around the world.