You are right, stock market may show you the public confidence in the social economy.
However, no evidence shows that it will keep the economy steady.
On the contrary, it will make the economy more volatile.
That's why there is artifical and manditory measure to stop any transaction when the stock price is going to be out of control.

Capital won't give up any chance of earning possible profit.
The motivation is relentless, although majority of the time, unwise.

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