It is impossible and impractical to retain it all. Some of it is irrelevant and has to be discarded. Other is specific to some of the features of the system but plays no essential role in others. The rest of the information turns out instead to be relevant to understand some important behaviour of the system. The process of abstraction and simplification that is involved in discarding and retaining information has to undergo the acid test of providing in the end a coherent picture of the structure and the behaviour of the system - or at least of the few features that one is willing to understand.
Economic systems display contradictory features.
On the one hand they are a remarkable example of robust self-organization. A number of features that lie in the very definition of an economic system such as the appearance of money seam to occur in an almost obliged and spontaneous way. Consumers, producers and traders appear to coordinate their actions in spite of the fact that they take their decisions acting independently, with incomplete information and based only upon independent needs and preferences. The system as a whole displays a high degree of order and many parameters appear as self-regulated. Major natural catastrophes or social transformations such as wars are absorbed showing little or no change in the expected values of many indicators a short time after their occurrence.