One world is (probably) just as good as many

One of our most sophisticated accounts of objective chance in quantum mechanics involves the Deutsch–Wallace theorem, which uses state-space symmetries to justify agents’ use of the Born rule when the quantum state is known. But Wallace argues that this theorem requires an Everettian approach to measurement. I find that this argument is unsound. I demonstrate a counter-example by applying the Deutsch–Wallace theorem to the de Broglie–Bohm pilot-wave theory.