trying to think of any past civilizations that closed the gap between rich and poor successfully without civil turmoil and blood. Can't think of any... the closest i can think of is the U.S. at the turn of the last century, when the monopolies and trusts got taken down a peg. Not sure it can be done again, but one has to hope.
“An imbalance between rich and poor is the oldest and most fatal ailment of all republics.” –Plutarch ancient Greek biographer (c. 46 – 120 CE)