You don't need to guess, the bounds are common sensical.

1. Too much inequality, and the risk is bloodshed. This is most of human society. 2. Too little, and you get communism, repression, or European stagnation. 3. U.S. is in the goldilocks zone. The goal is to make it so most people in society don't give up (Japan had this happen).

USD is a bit of a red herring. It does make our capital markets the most valuable in the world, and it does generate nearly endless demand for the dollar, but that's actually based on the wide scale belief that the U.S. is far and away the best arbiter of the world economy. The EU had a shot at that crown and absolutely wrecked it via over regulating.