While other American orchestras struggle mightily to survive, the Boston Symphony sails along. “The BSO audience is larger than those of other orchestras, and its subscriber base loyal. On top of that, the BSO’s endowment portfolio is outperforming others in its field, whose dwindling returns have forced orchestras to downsize. Meanwhile, BSO Inc. has balanced its budget, even running a few six-figure surpluses over the past five years.”