"These ideas have implications not only for theoretical and econometric practices but also for the ways in which policymakers and their advisers think about the choices confronting them. In particular, the rational expectations approach directs attention away from particular isolated actions and toward choices among feasible rules of the game, or repeated strategies for choosing policy variables. While Keynesian and monetarists macroeconomic models have been used to try to analyze what the effects of isolated actions would be, it is now clear that the answers they have given have necessarily been bad, if only because such questions are ill-posed."

"In contrast to Smith’s incomplete modeling, his follower, David Ricardo, provides a coherent setting— basically, the first macroeconomic model—that can be tested, modified, and applied. Although Ricardo is surely narrower and less imaginative and insightful than Smith, he is also a lot better organized. That is why Ricardo’s analysis of macroeconomics—for example, of the implications of public debt—is more coherent and useful than Smith’s."

"Policy models, aimed at analyzing actual macroeconomic policy issues. Models in this class should fit the main characteristics of the data, including dynamics, and allow for policy analysis and counterfactuals."

"The different classes of models have a lot to learn from each other, but the goal of full integration has proven counterproductive. No model can be all things to all people."

"The IS-LM model appears to describe well the behavior of the economy in the short run. In particular, the effects of monetary policy appear to be similar to those implied by the IS-LM model once dynamics are introduced in the model. An increase in the interest rate due to a monetary contraction leads to a steady decrease in output, with the maximum effect taking place after about eight quarters."

"Yes, IS-LM simplifies things a lot, and can’t be taken as the final word. But it has done what good economic models are supposed to do: make sense of what we see, and make highly useful predictions about what would happen in unusual circumstances. Economists who understand IS-LM have done vastly better in tracking our current crisis than people who don’t."

"The biggest step I ever made was, I guess, the "Expectations and the Neutrality of Money" paper in 1972, in the sense that this paper was for me and, (I think) for the profession, a big step from what other people had done. The economic logic of it was very much built on Phelps — the parable of an economy of islands — which wasn't my idea at all. But what Phelps got me thinking about was a general equilibrium model in which monetary shocks could induce people to work harder because of lack of information. It was a technically cool paper, it was hard to write, and it put me on the map as a theoretical economist."

"An important addition to this classical doctrine of factor-price equalisation has been supplied by Professor Bertil Ohlin. In his weighty Interregional and International Trade (1933), Ohlin has developed the highly interesting result that (1)free mobility of commodities in international trade can serve as a partial substitute for factor mobility and (2) will lead to a partial equalisation of relative (and absolute) factor prices. This important result, which we may call the Ohlin-Heckscher theorem, since Ohlin attributes it to a 1919 Swedish article by Professor E. F. Heckscher, has some foreshadowings in the literature of the last century."

"Economics is a science of thinking in terms of models joined to the art of choosing models which are relevant to the contemporary world. It is compelled to be this, because, unlike the typical natural science, the material to which it is applied is, in too many respects, not homogeneous through time. The object of a model is to segregate the semi-permanent or relatively constant factors from those which are transitory or fluctuating so as to develop a logical way of thinking about the latter, and of understanding the time sequences to which they give rise in particular cases. Good economists are scarce because the gift for using "vigilant observation" to choose good models, although it does not require a highly specialised intellectual technique, appears to be a very rare one."

"Many of the stories economists tell take the form of models—for whatever else they are, economic models are stories about how the world works."

"Economists also use models to learn about the world, but instead of being made of plastic, they are most often composed of diagrams and equations. Like a biology teacher’s plastic model, economic models omit many details to allow us to see what is truly important. Just as the biology teacher’s model does not include all the body’s muscles and capillaries, an economist’s model does not include every feature of the economy."

"In many parts of the economy, stabilizing forces appear not to operate. Instead, positive feedback magniﬁes the effects of small economic shifts; the economic models that describe such effects differ vastly from the conventional ones. Diminishing returns imply a single equilibrium point for the economy, but positive feedback – increasing returns – makes for many possible equilibrium points. There is no guarantee that the particular economic outcome selected from among the many alternatives will be the “best” one."

"The corporatist-economic model of society appears to be governing us. Economists, often in the pay of transnationals, are deciding, for us, what democracy is, and will be."

"Much of my work in this period was concerned with exploring the logic of economic models, but also with attempting to reconcile the models with every day observation."

"The striking parallel between the economic models that are currently under discussion and some engineering systems suggests the hope that in some way the rapid progress in the development of the theory and practice of automatic control in the world of engineering may contribute to the solution of the economic problems."

"Haavelmo was the ﬁrst to recognize the capacity of economic models to guide policies. This paper describes some of the barriers that Haavelmo’s ideas have had (and still have) to overcome, and lays out a logical framework that has evolved from Haavelmo’s insight and matured into a coherent and comprehensive account of the relationships between theory, data and policy questions. The mathematical tools that emerge from this framework now enable investigators to answer complex policy and counterfactual questions using simple routines, some by mere inspection of the model’s structure."

"The so-called free market does not provide consumers with proper information, because the social and environmental costs of production are not part of the current economic models. ...an ecological tax reform would be strictly revenue neutral, shifting the tax burden from income taxes to "eco-taxes." …the taxes would be added to existing products, forms of energy, services, and materials, so that prices would better reflect true costs."

"Unless the fundamental categories of economics such as ‘property’ were to be redefined in a radically personal way the liberal rationalist curse which had established economics as a scientific discipline cut off from human interests would proliferate. Economic models … have failed to incorporate any meaningful index of individual benefit other than the original utilitarian one, … the index of increasing income or an increasing flow of commodities."

"Unlike Hegel’s progress model of history, which moves by stages, each containing its own logic of growth and decline, the economic model develops as the simple function of one money-variable over time, with a long-term trend which increases monotonically."

"Real economic efficiency implies including all resources that affect sustainable human well-being in the allocation system, not just marketed goods and services. Our current market allocation system excludes most non-marketed natural and social capital assets and services that are critical contributors to human well-being. The current economic model ignores this and therefore does not achieve real economic efficiency. A new, sustainable ecological economic model would measure and include the contributions of natural and social capital and could better approximate real economic efficiency."

"The long term solution to the financial crisis is to move beyond the ‘growth at all costs’ economic model to a model that recognizes the real costs and benefits of growth."

"The construction of an economic model, or of any model or theory for that matter (or the writing of a novel, a short story, or a play) consists of snatching from the enormous and complex mass of facts called reality, a few simple, easily-managed key points which, when put together in some cunning way, become for certain purposes a substitute for reality itself."

"I view the work I've done related to statistics and economics as roughly speaking, how to do something without having to do everything. So economic models -- how any model by definition isn't right. When someone just says, 'Oh, your model is wrong.' That's not much of an insight. What you want to know is, is wrong in important ways or wrong in ways that are less relevant? And you want to know what does the data really say about the model?"