One trade is bound to another by the fact that they are each other's customers. High profits in one line increase the demand for the products of another line, and therefore its prices and wages. In addition to this bond, the lines are bound together by psychological ties. Men on a market act as men do in a crowd; they do not make their estimates independently and scientifically, but are much influenced by the general opinion or the opinion of certain leaders; others are wholly imitative, particularly the amateur speculator. For this reason an event which in theory should affect market values but slightly may actually cause rapid and wide fluctuations. Therefore overproduction in one or two lines, an event that is inevitable under our capitalistic system, followed by declining prices and security values, will occasion a bearish opinion that will infect the whole industry or market. This psychological factor not only broadens the scope and adds to the precipitancy of the panic, but it also accelerates the boom preceding a panic and holds the business world in a state of depression sometimes for an undue period after the panic.