Sociologists have often wondered about financial collapses, like those of the 1930s, in which rumors of insolvency, when believed by enough depositors, resulted in bank failures. What sociological concept describes this phenomenon?

the Thomas theorem

Explanation:

The Thomas theorem was a concept formulated first in 1928 by Isaac Thomas and Dorothy Swaine Thomas. Together they argue how situations can have strong consequences depending on the interpretation of situations which cause the real effect and drive the actions.

The facts are for them not so relevant as the beliefs & interpretation itself of what happens, then any rumours of insolvency or cases of bankruptcy resulted simply by the mere beliefs and other great financial collapses can be explained in terms of the Thomas theorem.

Beliefs and the way happenings are interpreted has a profound impact and consequences.