Great comment, thank you!
I put some thoughts down here for how to improve the world which relates to this discussion. I think as more people move up Maslow's Hierarchy of Needs the number of births will decline as people have better access to birth control and infant mortality rates decline.
I think the Giving Pledge will also play an important role in the future.
I am really taken back by the number of, and so many well recognized members in the Giving Pledge. That gives me a little more hope, and optimism is reappearing :-)
Must sleep now, but I definitely will read and comment on your How to Improve the World tomorrow.
Thanks! Following you for more.