Can we put a lid on this conflation of subjective probability with objective quantum branching please? A deterministic fair coin does not split the world, and neither would a deterministic economic cycle. Or are we taking seriously the possibility that the course of the economy is largely driven by quantum randomness?

I'm certainly taking it seriously, and am somewhat surprised that you're not. Some ways small-sized effects (most likely to "depend" of quantum randomness) can eventually have large-scale impacts:

• DNA Mutations
• Which sperm gets to the egg
• The weather
• Soft errors from cosmic rays or thermal radiation