The markets stopped crashing when enough measures were introduced to ensure the financial system would not fall apart.
Have govnuts got the tools to stop another crash? I do not know. They have transferred much of the financial sector risks and costs from the private sector onto the backs of taxpayers.
If govnuts print enough money then perhaps markets will not collapse, but instead go up but less than the rate of inflation (assuming that can be engineered).
Martis probably knows how far markets could fall, so I hope he answers your question. I have no idea. A guess is that the All Ordinaries could be back to around 2200 if the collapse involved China and a massive reduction in commodity prices and trade. Our speccies could fall by 80-90%. The gold price could fall 30-50% initially.
I hope my optimistic guesses help you sleep better.
