"The distinction between micro- and macro inventions matters because they appeared to be governed by different laws. Micro-inventions generally result from an intentional search for improvements, and are understandable -if not predictable- by economic forces. They are guided, at least to some extent, by the laws of supply and demand and by the intensity of search and the resources committed to them, and thus by signals emitted by the price mechanism. Furthermore, in so far as micro inventions are the by-products of experience through learning by doing or learning by using they are correlated with output or investment. Macroinventions are more difficult to understand, and seem to be governed by individual genius and luck as much as by economic forces. Often they are based on some fortunate event, in which an inventor stumbles on one thing while looking for another, arrives at the right conclusion for the wrong reason, or brings to bear a seemingly unrelated body of knowledge that just happen to hold the clue to the right solution. The timing of these inventions is consequently often hard to explain. Much of the economic literature dealing with the generation of technological progress through market mechanisms and incentive devices thus explain only part of the story. This does not mean that we have to give up the attempt to try to understand macroinventions. We must, however, look for explanations largely outside the trusted and familiar market mechanisms relied upon by economists."