Whatever mechanism is deemed fair by the majority. But I think we need to consider the size of our population as a factor in our global problem. Continued population growth is unsustainable. There has to be a limit. The Earth is a fixed size. There is a fixed quantity of water available. SInce there has to be a limit why is it fundamentally better to live on Earth with 12 billion people rather than 4 billion? At 8 billion we don't adequately feed the population we have now? Why live at a level that is stretching our resources to the breaking point?