Over the past fifty years or so we have seen a veritable fragmentation of economic theory. Research has ramified in different directions and its very foundations – methods and techniques of analysis, crucial concepts and simplifying assumptions, central problems – have undergone broad diversification. This has led to a division of labour among substantially autonomous groups of economists who often ignore, or in any case do not take into account in their own research, what happens in other areas of research. This trend has been reinforced by the high level of technicality that, together with diversification in the techniques of analysis, makes the studies required for any given field of research increasingly specific and time-consuming. For instance, the new evolutionary theories of the firm have no relation to research on the microeconomic foundations of macroeconomics; it would be quite difficult to find some common ground between research on the institutional evolution of financial markets and the so-called ‘new growth theory’ which seeks to make technical progress endogenous to the theory itself. Economists become ever more specialised and increasingly limit their readings and their professional contacts to researchers active in the same field and pursuing a similar research orientation; increasing numbers of specialised journals and professional societies are created; the very processes of academic selection favour the fragmentation of economists into separate corporations.
It is thus quite difficult, in this situation, to provide a reasonably balanced and complete illustration of the different streams of economic research.