A taxa natural de juros esta de volta ao centro do debate sobre política monetária, mas nem por isto a definição do quem vem a ser esta taxa é clara. O texto abaixo, do Federal Reserv Bank de São Francisco, é uma ótima introdução a este importante conceito.
A key question for monetary policymakers, as well as participants in financial markets, is: "Where are interest rates headed?" In the long run, economists assume that nominal interest rates will tend toward some equilibrium, or "natural," real rate of interest plus an adjustment for expected long-run inflation.
Unfortunately, the "natural" real rate of interest is not observable, so it must be estimated. Monetary policymakers are interested in estimating it because real rates above or below it would tend to depress or stimulate economic growth; financial market participants are interested because it would be helpful in forecasting short-term interest rates many years into the future in order to calculate the value and, therefore, the yields of long-term government and private bonds. This Economic Letter describes factors that influence the natural rate of interest and discusses different ways economists try to measure it.
Defining the natural rate of interest
In thinking about the natural rate of interest, economists generally focus on real interest rates. They believe that movements in those rates, more so than in nominal rates, influence businesses' decisions about investment spending and consumers' decisions about purchases of durable goods, like refrigerators and cars, and new housing, and, therefore, economic growth.
Over 100 years ago, Wicksell defined the natural rate this way:
There is a certain rate of interest on loans which is neutral in respect to commodity prices, and tends neither to raise nor to lower them. (1936 translation from 1898 text, p.102.)
Since then, various definitions of the natural rate of interest have appeared in the economics literature. In this Letter, the natural rate is defined to be the real fed funds rate consistent with real GDP equaling its potential level (potential GDP) in the absence of transitory shocks to demand. Potential GDP, in turn, is defined to be the level of output consistent with stable price inflation, absent transitory shocks to supply. Thus, the natural rate of interest is the real fed funds rate consistent with stable inflation absent shocks to demand and supply.
This definition of the natural rate takes a "long-run" perspective in that it refers to the level expected to prevail in, say, the next five to ten years, after any existing business cycle "booms" and "busts" underway have played out. For example, the U.S. economy is still at a relatively early part of its recovery from the 2001 recession, so the natural rate refers not to the real funds rate expected over the next year or two, but rather to the rate that is expected to prevail once the recovery is complete and the economy is expanding at its potential growth rate.
Para ler o texto completo, de autoria do John C. Williams, Senior Research Advisor: The Natural Rate of Interest (2003-32, 10/31/2003)
