Any kind of industrial policy, both domestically and in export subsidies only distorts the market by creating inefficiency and shifting resources from one sector to another of "unnatural" and completely unfair to industries and / or companies unselected.

For that perfect competition is a reality a number of assumptions must be met: no entry barriers to the industry should exist, offering good all companies must be uniform and must have perfect information and there should be no market power, no buyer and no seller should be able to influence the market price of the good.

It is easy to think of industries that are not perfectly competitive. The clearest cases are in high-tech industries such as aerospace, robotics and electronics, but it is not necessary that industries in which the well produced a very high price range as above.

Even in sectors where traditionally the well was perfectly homogeneous exchanged, such as food companies try to develop today through advertising product differentiation. Meanwhile, in developed sectors of consumer goods (household appliances, automobiles, beverages, etc.). Markets increasingly operate as monopolistic competition.

In masina fum greu service companies happens, something very similar. Insurance, banking and communications operators, among many others, try to differentiate the service provided to it by inventing new methods such as "quality", which adds to the increasingly sophisticated advertising.

In short, we found that the type of markets is very different (and increasingly) of perfect competition.
The problem for economists is that in this type of market, no one knows for sure how companies behave, unlike what happens in both perfect competition and the monopoly, in which it is relatively easy I predict.

Perfectly competitive firms, when faced with an infinitely elastic demand curve (are price takers), can only raise the price until it equals marginal cost while in monopoly enterprises, as they face a demand negative slope, they will raise the price in order to equalize the marginal revenue marginal cost (provided there are no laws that prevent), which market equilibrium will be at a point corresponding higher prices and fewer than in the competitive case.

But there is an extensive typology of markets that are halfway between those described above. Markets are characterized by imperfect competition and include all types of oligopoly and monopolistic competition all. The problem facing economists is that these markets are difficult to model, so for decades, economic theory has turned his back on them.

But from the sixties, he began to develop a new discipline within microeconomics that dealt with trying to explain how these markets work.