Question: What year did the author of The Tunnel win the William Dean Howells Medal?
Context: The Wapshot Scandal is a novel by American writer John Cheever, a follow-up to his National Book Award-winning "The Wapshot Chronicle".  It was Cheever's second published novel, and won the William Dean Howells Medal in 1965.  The scandal of the title involves one of the Wapshot wives running off with a 19-year-old bagboy from the local A&P and making a life with him in Italy. By Love Possessed is a novel written by James Gould Cozzens in the middle 1950s.  It was published on August 26, 1957, by Harcourt Brace and Company, and became a critically acclaimed best-seller.  In 1960, it was awarded the William Dean Howells Medal, an award given every five years to the best novel of the previous five years. Redtop – also spelled Red Top – is a historic Shingle Style house located at 90 Somerset Street, Belmont, Massachusetts.  It was designated a National Historic Landmark in 1971 for its association with writer and literary critic William Dean Howells (1837–1920), a leading proponent of realism in literature.  The Shingle Style house was designed by Howells' brother-in-law William Rutherford Mead, and served as the Howells' residence from its construction in 1877 to 1882. William Howard Gass (born July 30, 1924) is an American novelist, short-story writer, essayist, critic, and former philosophy professor.  He has written three novels, three collections of short stories, a collection of novellas, and seven volumes of essays, three of which have won National Book Critics Circle Award prizes and one of which, "A Temple of Texts" (2006), won the Truman Capote Award for Literary Criticism.  His 1995 novel "The Tunnel" received the American Book Award.  His 2013 novel "Middle C" won the 2015 William Dean Howells Medal. Elinor Mead Howells (May 1, 1837 – May 6, 1910) was an American artist, architect and aristocrat.  She was married to author William Dean Howells and designed the William Dean Howells House in Cambridge. The William Dean Howells House is a historic house at 36 Pepperrell Road in Kittery Point, Maine.  Built c. 1870, this house was for many years the summer residence of writer and editor William Dean Howells, best known as editor of "Atlantic Monthly" magazine.  The house was listed on the National Register of Historic Places in 1979 (where the listing misspells the name "Howels"). The William Dean Howells Medal is awarded by the American Academy of Arts and Letters.  Established in 1925 and named for William Dean Howells, it is given once every five years, generally in recognition of the most distinguished American novel published during that period, although some awards have been made to novelists for their general body of work.  The recipient of the award is chosen, by a committee drawn from the membership of the Academy, from among those candidates nominated by a member of the Academy. The Whole Family: a Novel by Twelve Authors (1908) is a collaborative novel told in twelve chapters, each by a different author.  This unusual project was conceived by novelist William Dean Howells and carried out under the direction of "Harper's Bazaar" editor Elizabeth Jordan, who (like Howells) would write one of the chapters herself.  Howells' idea for the novel was to show how an engagement or marriage would affect and be affected by an entire family.  The project became somewhat curious for the way the authors' contentious interrelationships mirrored the sometimes dysfunctional family they described in their chapters.  Howells had hoped Mark Twain would be one of the authors, but Twain did not participate.  Other than Howells himself, Henry James was probably the best-known author to participate.  The novel was serialized in "Harper's Bazaar" in 1907-08 and published as a book by Harpers in late 1908. Billy Bathgate is a 1989 novel by author E. L. Doctorow that won the 1989 National Book Critics Circle award for fiction for 1990, the 1990 PEN/Faulkner Award for Fiction, the 1990 William Dean Howells Medal, and was the runner up for the 1990 Pulitzer Prize and the 1989 National Book Award.  The story is told in the first person by Billy "Bathgate" Behan, a fifteen-year-old boy who first becomes the gofer and then surrogate son of mobster Dutch Schultz. The Tunnel is William H. Gass's 1995 "magnum opus" that took 26 years to write and earned him the American Book Award of 1996.  It was also a finalist for the PEN/Faulkner award.
Answer: 2015