There's not been too many as it's remarkably difficult to implement an alternative to a market economy outside of revolution. That likely favours specific alter

There's not been too many as it's remarkably difficult to implement an alternative to a market economy outside of revolution. That likely favours specific alternatives. I've not seen attempts to implement any approach that is seeking sustainability, or constrain growth, or break out of the duopoly of centrally planned vs free market. That leaves a lot of ideas, of varying credibility, that have never been trialled in any way, shape, or form. Off the top of my head "doughnut economics" was briefly popular in the news a few years ago. It remains a thought experiment. (I don't remember enough about it to comment on its viability).