James D. Hamilton

A New Approach to the Economic Analysis of Nonstationary Time Series and the Business Cycle.

This paper models occasional, discrete shifts in the growth rate of a nonstationary series. Algorithms for inferring these unobserved shifts are presented, a byproduct of which permits estimation of parameters by maximum likelihood. An empirical application of this technique suggests that the periodic shift from a positive growth rate to a negative growth rate is a recurrent feature of the U.S. business cycle, and indeed could be used as an objective criterion for defining and measuring economic recessions. The estimated parameter values suggest that a typical economic recession is associated with a 3 percent permanent drop in the level of GNP. Copyright 1989 by The Econometric Society.

Oil and the Macroeconomy since World War II

All but one of the U.S. recessions since World War II have been preceded, typically with a lag of around three-fourths of a year, by a dramatic increase in the price of crude petroleum. This does not mean that oil shocks caused these recessions. Evidence is presented, however, that even over the period 1948-72 this correlation is statistically significant and nonspurious, supporting the proposition that oil shocks were a contributing factor in at least some of the U.S. recessions prior to 1972. By extension, energy price increases may account for much of post-OPEC macroeconomic performance.

Analysis of time series subject to changes in regime

Abstract This paper introduces an EM algorithm for obtaining maximum likelihood estimates of parameters for processes subject to discrete shifts in autoregressive parameters, with the shifts themselves modeled as the outcome of a discrete-valued Markov process. The simplicity of the EM algorithm permits potential application of the approach to large vector systems.

Autoregressive conditional heteroskedasticity and changes in regime

ARCH models often impute a lot of persistence to stock volatility and yet give relatively poor forecasts. One explanation is that extremely large shocks, such as the October 1987 crash, arise from quite different causes and have different consequences for subsequent volatility than do small shocks. We explore this possibility with U.S. weekly stock returns, allowing the parameters of an ARCH process to come from one of several different regimes, with transitions between regimes governed by an unobserved Markov chain. We estimate models with two to four regimes in which the latent innovations come from Gaussian and Student t distributions.

What is an Oil Shock

This paper uses a flexible approach to characterize the nonlinear relation between oil price changes and GDP growth. The paper reports clear evidence of nonlinearity, consistent with earlier claims in the literature-- oil price increases are much more important than oil price decreases, and increases have significantly less predictive content if they simply correct earlier decreases. An alternative interpretation is suggested based on estimation of a linear functional form using exogenous disruptions in petroleum supplies as instruments. The evidence suggests that oil shocks matter because they disrupt spending by consumers and firms on certain key sectors.

This is what happened to the oil price-macroeconomy relationship

Abstract Many of the quarterly oil price increases observed since 1985 are corrections to even bigger oil price decreases the previous quarter. When one looks at the net increase in oil prices over the year, recent data are consistent with the historical correlation between oil shocks and recessions.

Rational-expectations econometric analysis of changes in regime: An investigation of the term structure of interest rates

Abstract This paper is of interest both for its methodological contribution of new tools for analyzing rational-expectations models and for its substantive conclusions concerning the term structure of interest rates during the monetary experiment of October 1979. The paper studies systems subject to changes in regime, interpreted here as occasional, discrete shifts in the parameters governing the time series behavior of exogenous economic variables. The specification is shown to be quite tractable both theoretically and empirically. The technique is used to analyze yields on three-month Treasury bills and ten-year Treasury bonds during 1962 to 1987. A constant-parameter linear model for short-term rates is shown to be inconsistent both with the univariate time series properties of short rates and with the observed bivariate relation between long and short rates under the expectations hypothesis of the term structure. AN alternative nonlinear model that admits the possibility of changes in regime affords a much better description of the univariate process for short rates. Moreover, the cross-equation restrictions implied by the expectations hypothesis of the term structure are consistent with the nonlinear specification. Indeed, the residuals of the restricted relation have a standard error of only 0.8 basis points. This is a third less than that of a completely unrestricted linear regression of long rates on short rates, and compares with an unconditional standard deviation of long rates of 142 basis points. I conclude that once the recognition by bond traders of changes in regime is taken into account, the expectations hypothesis of the term structure of interest rates holds up fairly well for these data.

Causes and Consequences of the Oil Shock of 2007-08

This paper explores similarities and differences between the run-up of oil prices in 2007-08 and earlier oil price shocks, looking at what caused the price increase and what effects it had on the economy. Whereas historical oil price shocks were primarily caused by physical disruptions of supply, the price run-up of 2007-08 was caused by strong demand confronting stagnating world production. Although the causes were different, the consequences for the economy appear to have been very similar to those observed in earlier episodes, with significant effects on overall consumption spending and purchases of domestic automobiles in particular. In the absence of those declines, it is unlikely that we would have characterized the period 2007:Q4 to 2008:Q3 as one of economic recession for the U.S. The experience of 2007-08 should thus be added to the list of recessions to which oil prices appear to have made a material contribution.

Stock market volatility and the business cycle

This paper investigates the joint time series behavior of monthly stock returns and growth in industrial production. We find that stock returns are well characterized by year-long episodes of high volatility, separated by longer quiet periods. Real output growth, on the other hand, is subject to abrupt changes in the mean associated with economic recessions. We study a bivariate model in which these two changes are driven by related unobserved variables, and conclude that economic recessions are the primary factor that drives fluctuations in the volatility of stock returns. This framework proves useful both for forecasting stock volatility and for identifying and forecasting economic turning points. Copyright 1996 by John Wiley & Sons, Ltd.

Oil Shocks and Aggregate Macroeconomic Behavior: The Role of Monetary Policy*

A recent paper by Bernanke, Gertler, and Watson (1997) suggests that monetary policy could be used to eliminate any recessionary consequences of an oil price shock. This paper challenges this conclusion on two grounds. First, we question whether the Federal Reserve actually has the power to implement such a policy; for example, we consider it unlikely that additional money creation would have succeeded in reducing the Fed funds rate by 900 basis points relative to the values seen in 1974. Second, we point out that the size of the effect that Bernanke, Gertler, and Watson attribute to oil shocks is substantially smaller than that reported by other researchers, primarily due to their choice of a shorter lag length than that used by other researchers. We offer evidence in favor of the longer lag length employed by previous research and show that under this specification, even the aggressive Federal Reserve policies proposed would not have succeeded in averting a downturn.