بانکهای مرکزی از تئوری اقتصاد کلان مدرن چه چیزی آموخته اند ؟

In this essay I argue that modern macroeconomic theory has fallen behind the practice of central banking. After briefly summarizing the current state of macro theory, I focus on what strikes me as the two most important developments in monetary policy in the last two decades – inflation targeting and dealing with financial crises. My analysis rejects the claims made by several authors to the effect that the proliferation of inflation-targeting regimes around the globe represents an application of well-established principles of macroeconomic theory. As for how monetary policy can promote financial stability, a subject on which most economists agree modern theory has been of little help, I argue that macroeconomics has lost touch with the fundamental raison d’être of central banking. My diagnosis is that macroeconomic theory has become distracted by its preoccupation with states of equilibrium, a preoccupation that inhibits analysis of a market economy’s coordination mechanisms. I conclude with a plea for a more diverse ecology of approaches to macroeconomic theory, one that finds room for agent-based computational economics as well as for more conventional equilibrium theories.

Technological innovation in today’s world draw heavily on fundamental science. But the connection between science and technology was not always like this. Economic historians have long argued that the key technologies of the first Industrial Revolution owed nothing to scientific theory; that many of the inventions were made by “tinkerers” with no formal scientific education.1 Indeed Rosenberg (1982) makes the case that, even well into the 20th Century, the causal link between science and technology was often the reverse of what we now take for granted; that scientific knowledge was the result, as much as or even more than it was the cause, of technological breakthroughs. For example, the science of aerodynamics was not sufficiently advanced to explain why birds can fly until the Wright brothers found out how to make humans fly; Vane discovered the principles underlying aspirin’s anti-thrombotic effect only after practicing physicians had already discovered that the effect exists and had even begun prescribing aspirin for the prevention of heart attacks and strokes. Indeed, entire fields of scientific inquiry arose from discoveries made in the course of solving practical technological problems, such when Pasteur’s attempts to deal with putrefaction in his family wine business opened up the field of microbiology, or when the knowledge generated by German dye-makers provided the clues that formed the basis of organic chemistry. In these and many more cases described by Rosenberg, practitioners had a lot more to teach theorists than the other way around; the practitioners discovered what works, and the theorists scrambled to keep up, looking for general covering laws that might explain why it works. My purpose in this essay is to investigate the relationship between practitioners and theorists of monetary policy. Have central bankers, the practitioners, been applying developments of modern macroeconomic theory, as the developers of modern computer technology have been applying solid state physics and other branches of scientific theory, or has macroeconomic theory been lagging behind practice, as scientific theory did in the first Industrial Revolution? I will argue that, despite the impressive technical progress that macroeconomics has made, and despite the fact that the profession seems to have reached a consensus on methodology that allows it to move beyond the polemics that once characterized the subject, nevertheless macroeconomic theory has fallen behind the practice of central banking. After briefly summarizing the current state of macro theory, I will focus on what strike me as the two most important developments in monetary policy in the last two decades – inflation targeting and dealing with financial crises. My analysis rejects the claims made by several authors to the effect that the proliferation of inflation-targeting regimes around the globe represents an application of well-established principles of macroeconomic theory. As for how monetary policy can promote financial stability, a subject on which most economists agree modern theory has been of little help, I argue that macroeconomics has lost touch with the fundamental raison d’être of central banks. My diagnosis is that macroeconomic theory has become distracted by its preoccupation with states of equilibrium, a preoccupation that inhibits analysis of a market economy’s coordination mechanisms. I conclude with a plea for a more diverse ecology of approaches to macroeconomic theory, one that finds room for agent-based computational economics as well as for more conventional equilibrium theories.

This is not an argument for scrapping DSGE models altogether. On the contrary, when we understand as little as we do about macroeconomic systems, we need all the tools we can get. Moreover, even if modern new Keynesian DSGE theory does not represent a significant improvement over old Keynesian economics, it does embody much of the wisdom that has accrued from the history of central banking. But it does not embody all of that wisdom. What central bankers and other policy makers need from macroeconomic theory at this point is a broader variety of approaches, so that they can see their problems from more than one angle, especially those problems that are hard to address using the currently popular mainstream approach. Fortunately I sense an increased willingness in the profession to satisfy that need for a diversity of approaches, now that the financial crisis and the great recession have shaken belief in the modern consensus. Whether this increased willingness will result eventually in a more useful array of theoretical frameworks is yet to be seen. Meanwhile, modern macroeconomic theory has more to learn from central bankers than it has to teach them.