When we talk about economics, multiple actors control those mechanisms.

We must consider that making trusted predictions about economics is not even possible. There are many things. 

That controls those economic mechanisms. There are many mathematical models of how economics and stock marketing should work. But the psychological effect breaks them all. The thing that makes us humans causes a fall in the stock market and endangers our economic environment. When we go to panic we just make things that don't seem reasonable. When we want to save our currencies we move money out of some country. 

When people make their decisions about buying and selling. They must be fast. That means people who work in stock marketing don't look at newspapers or news. They must follow the screen that shows exchange values. 

If some companies become cheaper. It loses its value. That means.

If there are more stocks free to buy. That decreases their value. Stocks behave like money. More money on marketing makes the value of money decrease. The relationship between money and stocks determines the value of stock marketing. 

So there are more stocks free compared to the money. That wants to buy those stocks. But willing to buy is measured by real buying. So other people see that willing only if the money or owner of money bought some stocks. And the same way willingness to sell is seen, only when somebody sells stocks or releases them. 

This is the reason why stock marketing goes into a panic. When somebody sells lots of stocks. 

That decreases their value. If some other people do not buy them. 

When people want to make money in stock marketing they will sell and buy stocks in a very short period. In that trade moves millions or even billions of dollars. When some stock marketing falls people can try to save money by transporting them to another country. And that is the thing that shakes the economy. 

Even short-period decreases in that level cause very big losses. So, when those people who own those capitals see that company's courses turned down. That forces those people to react to those curves. When some stocks turn down they must make a decision do they sell or do they wait just 15 seconds? There can be orders that are connected to some capital that the trader must sell them. If lots of stocks are released that decreases curves. And forces people to sell them.