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Thursday, November 24, 2005

NBER Papers on Declining GDP Volatility and the Bias in the CPI

Robert Gordon explores the reasons for the decline in business cycle volatility since the mid-1980s:

What Caused the Decline in U.S. Business Cycle Volatility?, by Robert J. Gordon , NBER WP 11777, November 2005: Abstract This paper investigates the sources of the widely noticed reduction in the volatility of American business cycles since the mid 1980s. Our analysis of reduced volatility emphasizes the sharp decline in the standard deviation of changes in real GDP, of the output gap, and of the inflation rate. The primary results of the paper are based on a small three-equation macro model that includes equations for the inflation rate, the nominal Federal Funds rate, and the change in the output gap. The development and analysis of the model goes beyond the previous literature in two directions. First, instead of quantifying the role of shocks-in-general, it decomposes the effect of shocks between a specific set of supply shock variables in the model’s inflation equation, and the error term in the output gap equation that is interpreted as representing “IS” shifts or “demand shocks”. It concludes that the reduced variance of shocks was the dominant source of reduced business-cycle volatility. Supply shocks accounted for 80 percent of the volatility of inflation before 1984 and demand shocks the remainder. The high level of output volatility before 1984 is accounted for roughly two-thirds by the output errors (demand shocks) and the remainder by supply shocks. The output errors are tied to the paper’s initial decomposition of the demand side of the economy, which concludes that three sectors - residential and inventory investment and Federal government spending, account for 50 percent in the reduction in the average standard deviation of real GDP when the 1950-83 and 1984-2004 intervals are compared. The second innovation in this paper is to reinterpret the role of changes in Fed monetary policy. Previous research on Taylor rule reaction functions identifies a shift after 1979 in the Volcker era toward inflation fighting with no concern about output, and then a shift in the Greenspan era to a combination of inflation fighting along with strong countercyclical responses to positive or negative output gaps. Our results accept this characterization of the Volcker era but find that previous estimates of Greenspan-era reaction functions are plagued by positive serial correlation. Once a correction for serial correlation is applied, the Greenspan-era reaction function looks almost identical to the pre-1979 “Burns” reaction function! [Open link to conference version of paper.]

Robert Gordon and Todd vanGoethem ask if there is a downward bias in the CPI:

A Century of Housing Shelter Prices: Is There a Downward Bias in the CPI?, by Robert J. Gordon, Todd vanGoethem, NBER WP 11776, November 2005: Abstract Tenant rental shelter is by far the most important component of the CPI, because it is used as a proxy for owner-occupied housing. This paper develops a wide variety of current and historical evidence dating back to 1914 to demonstrate that the CPI rent index is biased downward for all of the last century. The CPI rises roughly 2 percent per year slower than quality-unadjusted indexes of gross rent, setting a challenge for this research of measuring the rate of quality change in rental apartments. If quality increased at a rate of 2 percent per year, the CPI was not biased downward at all, but if quality increased at a slower rate of 1 percent per year, then the CPI was biased downward at a rate of 1 percent. Our analysis of a rich set of data sources goes backward chronologically, starting with a hedonic regression analysis on a large set of panel data from the American Housing Survey (AHS) covering 1975-2003. Prior to 1975, we have large micro data files from the U. S. Census of Housing extending back to 1930. In addition to the hedonic regression data, we stitch together data on the diffusion of important quality attributes of rental units, including plumbing, heating, and electrification, over the period 1918-73. Our final piece of evidence is based on a study of quality-adjusted rents in a single local community, Evanston IL, covering the period 1925-99. Our overall conclusions are surprisingly consistent across sources and eras, that the CPI bias was roughly -1.0 percent prior to the methodological improvements in the CPI that date from the mid-1980s. Our reliance on a wide variety of methodologies and evidence on types of quality change and their importance, while leaving the outcome still uncertain, at least in our view substantially narrows the range of possibilities regarding the history of CPI bias for rental shelter over the twentieth century. [Open link to earlier version.]

    Posted by on Thursday, November 24, 2005 at 01:01 AM in Academic Papers, Economics, Inflation | Permalink  TrackBack (0)  Comments (0)


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