How much money stays "always on", and how much money "can get out" in the stock market?

Are you asking how much of the total stock market capitalization is owned through mutual funds? It is estimated that about half, or a little more, of all the money invested in the stock market is through mutual funds or pension funds.

Not sure excatly what you are asking, but the simply fact is that when there are more buyers than sellers, prices rise. When there are more sellers than buyers, prices will drop. You can only sell when you have a buyer. "Everybody" cannot get out, it isn't possible. Millions of people who don't understand this can have their net worth disappear quickly. It happened in 1999. The market is a HUGE legalized pyramid scheme. You can only sell if there are buyers. IF something caused a huge selling wave and more people got scared as a result, the market will fall faster than a meteor heading towards earth. Paper profits can disappear REALLY REALLY fast. The 1930's depression would look like a good economy if things really fell apart now. It's REALLY scary if you think about it. The market is based on the greater fool theory, pushing prices higher and higher, with no regard for value. Google that didn't exist about 10 years ago is now valued at about $169 BILLION today. Coca Cola was founded in 1886 and has a market cap of $121 Billion, Disney has a Cap of $68 Billion. It's not real money,, it's all on paper.