10%,20%,30%,...it won't stop. I trust after a threshold, people can't survive in society. maybe prices of food just raise to make sure people can't live because other part of people notice that they don't need to let people live in world.
That's assuming that society just sits back and dies helplessly while we surpass 30% unemployment. In the Great Depression, that's not what happened; rather, we got a dramatic surge in organized labor, the New Deal, and World War Two. We can expect a similarly dramatic restructuring of global society when economic conditions get that bad again. People's reaction to food prices exceeding what they can afford doesn't tend to be "darn, I guess I will just starve then".
I hope so, but last time we still need human workers. Is this our best project that maybe people will do benevolent thing when enough people's life becoming terrible?