However the internet bubble and that of the

"The efficient market hypothesis was reconsidered from the 1987 crash." Here are the conceptual shift and the articles which the challenge. That year, the stock market has lost 26 without new information or a change in the fundamentals could justify. Before there was talk of market anomalies, but it was attacking not fundamentally the concept of the speculator as it had defined Milton Friedman: there is money to be done as soon as prices deviate from their fundamental. Starting from the principle that someone who sees a ticket of one hundred dollars by Earth picks up, individuals do not let go from opportunity to arbitrations. Since it was understood that this design is a little too simplistic because it did not take into account the concept of risk. People systematically collect the ticket if there is no risk, but most of the time there is a risk and market dealers do not all have the same ability to take risks. Paradoxically, the markets are thus the most efficient where there at least needs (at zero risk), and the less efficient where there in the most need (at risk).

If they try to estimate the relative to that of Microsoft Apple price, dealers are doing about well; it relatively estimate than gold or wood, it becomes more complicated. The error of the protagonists of the efficiency of the markets has been to argue that the markets are still efficient in all situations. It seems today that the markets are roughly competitive - we win rarely money without taking risk - and in these conditions the awards embody. Conversely, in Europe, as soon as prices do not, the markets are said inefficients! And when the Cds on the Greece (on Greek debt insurance) flaming, it is said that it is the fault to the speculators.

In fact the real problem of markets is that they just easier than pessimism optimism. It is easy "to be long" (bet upward) that "court" (bet the downward). But their most valuable role is to announce the bad news, the news everywhere have the most difficulty in movement. Valid markets as in business, telling his boss that it's going wrong is more complicated than to announce that the targets are exceeded. Even for the media it is more difficult. Enron has for example try to put pressure on Fortune magazine does not publish the investigation revealing his misdeeds.

In this regard, the history of ideas shows that when new facts come to question the existing ideas, eventually they change at empty their initial meaning. When we speak today of efficient markets should clarify what it is talking about. If it is to say that it is difficult to make money without taking an additional risk, then the hypothesis is true. When a MBS (mortgage-backed title) has a higher yield than a duty of State, one must ask why. A tenant of the efficient market hypothesis would say you that a superior performance involves a higher risk. This should be taught in high school. Also rated titles which give a different performance, is that one is more risky than the other. If answer you, there is no risk, is that it you ment, point.

In contrast, to refer to the efficiency of the markets by saying that the price is a reflection of the fundamental, is more philosophy than of a scientific proposal. Because unless you have a model of the Basic, you cannot verify the hyptohèse; and if you reject the you do not know if the hypothesis itself or the basic template that you reject.

If the role of the awards given by the market to allocate resources, the question becomes, what is price give good signal This is unfortunately not always the case. And the crisis has just tell us how it can be expensive to be wrong. The crash of 1987 clearly proven that prices did not reflect fundamental, whatever they are, because no model can explain variation in 26 without new information. At the time, the economic consequences have not been dramatic. However, the internet bubble and that of the