The big difference now is that the Fed is propping up a bubble using currency which they can create in unlimited quantities... This means that they can keep stock prices (denominated in that currency) going up forever and ensure that they never crash.

The only possible symptoms of the Fed's policy of artificially propping up the stock markets will be:

- Accelerating increase in the value of all scarce assets like gold, silver, cryptocurrencies, high-end real estate and stocks.

- People leaving their countries to relocate to places where asset values are less inflated and costs of living are lower; this would lead to significant capital flight.

- Accelerating wealth inequality.

- Civil unrest.

- Bitcoin could become the world's reserve currency instead of the US Dollar.

But a stock price crash is just not going to happen unless the Fed wants it to happen.

They will have to weigh up the possibility of allowing the stock market to crash against the risks alluded to above.

The main concerns which will guide their decision to let the stock market crash or not will be capital flight, civil unrest and USD losing its status as reserve currency of the world. Inequality is not much of a concern for them.