The League of American Orchestras has published its survey ("not meant to be comprehensive") of American orchestra premieres in the 2012-2013 season: It's an interesting and somewhat depressing reading.
According to LAO, "the list demonstrates the artistic vitality of orchestras across the continent," but if you look up San Francisco Symphony, you will see two (2) world premieres — Mark Volkert's Pandora and the Debussy/Robin Holloway Poems of Paul Verlaine for Renée Fleming — and two U.S. premieres, no more.
Meanwhile, smaller and poorer Seattle Symphony lists seven (7) world premieres. Where does artistic vitality reside?