What term describes a system that favors rich over poor?
In contemporary English, one sees the expression: the system is rigged against the poor; a rigged system.
This was a term used by Bernie Sanders in the US election: rigged economy.
But "a rigged system" can apply to many things, including voting.
It's such an interesting term as it dates back to the rigging of ship's sails. Elections are also said to be rigged.
All dictionaries give the two meanings: re ships and how something can be set up dishonestly to benefit the few. When you look at a tall ship, fully rigged, you can see how the term came to mean what it does: full-rigged sailing vessel
Here's the Merriam Webster's definition: rig
On sailing ships (tall ships), it is the captain who orders sailors to set the rigging (all the lines to sails and which sails are furled or unfurled) to his (or her!) own liking. As such, they control the ship and how it is sails through the sea(s).
One can say that captains have total say over the rigging. And in the literal sense, it does not mean what it has come to mean today in politics, economics, etc. where such a negative connotation remains of what is actually a beautiful thing. [There are many tall ship events around the world and its an amazing sight to see these old vessels sailing into a harbor. In fact, you can go on some of them and they will teach you how to rig the sails!]