Learning, as studied by psychologists, closely resembles sequential analysis in some aspects. Learning experiments usually consist of a series of tri… - Kenneth Arrow

In view of the magnitude of an economic system, it would take only a very small percentage of improvement in economic stability or growth to make almost any conceivable data collection worthwhile. The situation is analogous to reported results of the use of linear programming in industry; the gains are small in proportion to previous profit levels but still very much larger than the costs of the programming. No country is adequate in respect to its data. In particular the underdeveloped countries, with their ambitious programs, might well ponder whether or not the marginal productivity of investment in better economic statistics is perhaps not higher than almost any conceivable alternative; they have more need and fewer data.

Social theories are also social facts. Whatever explanatory value the “Marxist” or “conservative” models may have, they surely cannot be regarded as established with any degree of firmness. Yet excessive confidence in one or the other may have serious consequences. If “conservatives” believe too strongly that any move to socialism undermines democracy, then they may indeed act in accordance with the “Marxist” model, and vice versa. (Robert Merton long ago alerted us to “self-confirming” and “self-denying” social theories; here we have a pair of rival theories which are “other-confirming.”)

General competitive equilibrium above all teaches the extent to which a social allocation of resources can be achieved by independent private decisions coordinated through the market. We are assured indeed that not only can an allocation be achieved, but the result will be Pareto efficient. But, as has been stressed, there is nothing in the process which guarantees that the distribution be just. Indeed, the theory teaches us that the final allocation will depend on the distribution of initial supplies and of ownership of firms. If we want to rely on the virtues of the market but also to achieve a more just distribution, the theory suggests the strategy of changing the initial distribution rather than interfering with the allocation process at some later stage.