If economists wished to study the horse, they wouldn't go and look at horses. They'd sit in their studies and say to themselves, "what would I do if … - Ronald Coase

Why... are there any market transactions at all? Why not all production carried on by one big firm?... First, as a firm gets larger, there may be decreasing returns to the entrepreneur function, that is, the costs of organizing additional transactions within the firm may rise... Second, it may be that as the transactions which are organized increase, the entrepreneur fails to place the factors of production in the uses where their value is greatest, that is, fails to make the best use of the factors of production... Finally, the supply price of one or more of the factors of production may rise, because the "other advantages" of a small firm are greater than those of a large firm.

I can't remember [of a good regulation]. Regulation of transport, regulation of agriculture—agriculture is a, zoning is z. You know, you go from a to z, they are all bad. There were so many studies, and the result was quite universal: The effects were bad.

But a theory is not like an airline or bus timetable. We are not interested simply in the accuracy of its predictions. A theory also serves as a base for thinking. It helps us to understand what is going on by enabling us to organize our thoughts. Faced with a choice between a theory which predicts well but gives us little insight into how the system works and one which gives us this insight but predicts badly, I would choose the latter, and I am inclined to think that most economists would do the same.