No one knows
It just takes a very small pointy object to burst a real balloon, the economy is no different
It is like the story of the couple that want to get divorced and the Lawyer says why? and she says "he will not put the cap on the toothpaste" So it is the "straw that breaks the camels back"
To me the sure signs are when the peoples confidence breaks, which IMHO is why we have all been "desensitized" and "dumbed down" so that we don't react unless the sky starts to actually fall
You see it with shares, when the company has a disaster but some "head" comes out and says there is nothing wrong, so the price of the shares jumps up !!!