These so called "bubbles" are purely psychological because they are based on imaginary abstractions.
>This was the situation of the Great Depression when here we were still, in a material sense, a very rich country, with plenty of fields and farms and mines and factories...everything going. But suddenly because of a psychological hang-up, because of a mysterious mumbo-jumbo about the economy, about the banking, we were all miserable and poor - starving in the midst of plenty. Just because of a psychological hang-up. And that hang-up is that money is real, and that people ought to suffer in order to get it. But the whole point of the machine is to relieve you of that suffering. It is ingenuity. You see we are psychologically back in the 17th century and technically in the 20th. And here comes the problem. So what we have to find out how to do is to change the psychological attitude to money and to wealth and further more to pleasure and further more to the nature of work. And this is a formidable problem.
-Alan Watts: Money, Guilt, and the Machine