The title of your post suggests you think we are in very real danger of reaching the limit, whatever it is. Yes, technology is what has always allowed us to support more people with less work. At one time, the labor of one person was needed to support one person. Now the labor of one person plus steel, internal combustion, telephonic, and penicillin support many more. Imagine a small community of families, all of whom must work in a mine in order to eat. Then burros are introduced. The men and some burro technology can now do the work of two people. Women are free to stay home and make babies. But once they do, they have to stay there. To make sure the babies dont eat soap and die. One child dies, population decline. The mother is now free to become a schoolmarm and take in all the children. The other mothers go back to the mine. Production doubles. Wealth doubles. Dads get old and start to die. Population decline. Educated kids replace burros with pulleys and levers. Production doubles. Wealth doubles. The X Box is invented. Grandparents tell grandkids, "In my day, all teenagers worked to maintain a sustenence farm. Now your dad and his satellite navigated tractor can feed scores of people, so all you punks do is play your Grand Auto Theft. Forget about labor saving technology and food production technology. Isn't it likely that one small breakthrough forty years from now that makes desalinating water cheaper than wells and canals and pipelines could make it possible for Tunisia not only to support five times as many people, but raise them to prosperity by raising so much mutton that the price in Bhutan falls by half, and people there dont have to worry about elder care? What if, like in the last forty years, the next forty bring countless thousands of similar discoveries? Today, you work to support yourself and a vast transportation infrastructure. What if in forty years you can do your work from home, travel 1/20th as much, and your community needs 1/20th as many pilots, airplane waitresses, air traffic controllers, runway pavers, and airport firemen? Wouldnt those people do other work that would support people other than you?