NEW YORK--(BUSINESS WIRE)--Tiffany & Co. today announced that it has signed a long-term partnership agreement with the Whitney Museum of American Art to be the lead sponsor of the Whitney Biennial, the foremost exhibition of contemporary American art with an illustrious history of discovering new artists. The agreement calls for Tiffany to sponsor the next three biennials in 2017, 2019 and 2021. The 2017 exhibition will be the first held in the new Whitney Museum, designed by celebrated arc