A monthly crude oil spot price forecasting model using relative inventories
Introduction
In this paper, we develop a simple and practical model for forecasting monthly crude oil spot prices under normal market circumstances1 using readily available data. The objective of this model is to provide a dynamic forecast of monthly West Texas Intermediate (WTI) prices for the post Gulf War I time period using readily available data (WTI spot prices and OECD petroleum inventories) readily available and that can be implemented in spreadsheet applications. Thus, the model is intuitively appealing and useful to industry and government decision-makers in forecasting prices and in investigating the impacts on price of changing market fundamentals, such as petroleum inventories, production, imports, and demand. Because of the few variables involved, the results from the forecast model can be easily interpreted. The model is also practical from a maintenance standpoint in that it is based on two readily available data series.
We focus on the concepts of normal and relative levels of petroleum market variables such as demand, field production, net imports, and inventory. This is similar to the natural rate theory widely applied in macroeconomic modeling and empirical studies. We decompose the observed level of a petroleum market variable into two components: the normal level, determined by historical seasonal movements and trends, which reflects the normal market demand and operational requirements; and the relative level, the difference between the observed and normal levels, which reflects short-run market fluctuations. Seasonality exists in petroleum market variables such as demand, field production, and net imports. Since change in inventory equals the difference between demand and supply (the sum of field production and net imports), petroleum inventory demonstrates seasonal movements as well. Long-term inventory trends exist due to the trends in government inventories, increases in long-term product demand, and the larger distribution and storage infrastructure needed to meet demand growth and product differentiation. It is the relative levels of demand, field production, net imports, and inventory that respond to the unexpected short-run variations in the market.
Among these relative level variables, it is the relative inventory that matters most in the short run for the determination of crude oil price.2 On the demand side, many consumers have few options and little discretion as to how much volume they can use in the short term. People must heat their homes in the winter and drive to work regardless of price. This implies that short-term demand elasticity is small. On the supply side, supply chains that move crude oil from its source of production to refineries, and then move product from refineries to consumers, are long and cannot be adjusted quickly when unexpected shifts in supply or demand occur. Empirically, we have found that the short-run demand elasticity is indeed much less than the short-run inventory elasticity in the United States and the production elasticity is virtually zero. Since total petroleum inventory levels are a measure of the balance, or imbalance, between petroleum production and demand, they reflect changing market pressures on crude oil prices, and thus provide a good market barometer for crude oil price change in the short run. Intuitively, relative inventory levels must be negatively related to prices, with distributed lagged effects.
The observed behavior of WTI spot prices and total OECD industrial inventories since Gulf War I supports this argument. The large swings in WTI spot prices during the late 1990s are coupled with counter-swings in OECD total inventories, particularly when measured in relative terms. For example, in 1998 production consistently exceeded demand; as a result, inventories grew to unusually high levels. Demand growth slowed during this period in part due to warm winters in the Northern Hemisphere and the Asian financial crisis, while supply increased substantially as Iraqi crude oil came back into the export market in 1997 through the “Oil-for-Food” Program. WTI spot prices fell to near $10 per barrel by the end of 1998 due to the excess of production over demand and the resulting inventory build. The supply/demand balance reversed in 1999 when OPEC cut back production to a level well below demand, and the demand for crude oil simultaneously increased as the Asian economies recovered. With demand exceeding production during 1999, inventories were drawn down to help meet demand. The excess inventories that had been built up fell rapidly to well below normal levels, and WTI spot prices correspondingly rose to over $30 per barrel by early March 2000. More recently, we have observed that the loss of Venezuelan crude oil production during the oil workers' strike in that country resulted in a large drop in U.S. crude oil inventories, while demand changed very little, even though crude oil prices climbed about $5 per barrel.3
Section snippets
A forecast model
The basic idea underlying the forecast model is the natural rate theory. Theoretically, the normal inventory level is determined by normal demand and normal operating requirements, while the relative inventory level responds to market fluctuations. For practical purposes, we calculate the normal inventory level by appropriately de-seasonalizing and de-trending historical data.4
Forecast evaluation
To evaluate the relative inventory (RSTK) model developed in the last section, we compare in-sample and out-of-sample forecast results with two alternative models. The first alternative model is a naïve autoregressive forecast (NAIV) modelin which AR(1) and AR(12) are the 1st-order and 12th-order autoregressive terms, respectively. Other variables are as defined in Eq. (3) to ensure comparability. Table 3 shows the estimates for the naïve model's
Conclusion
This paper presents and evaluates a simple and practical dynamic forecast model using petroleum inventories as the only independent variable.19 This practical model is needed because we found that existing simple models lack a theoretical basis and more complex models (in the general equilibrium
Acknowledgements
This work is partially sponsored by the Office of Petroleum Reserves, U.S. Department of Energy. The authors thank two anonymous referees for many helpful comments.
Michael YE teaches economics at St. Mary's College of Maryland. He has experience as a consultant to a wide variety of private and government organizations, including the U.S. Department of Defense and U.S. Department of Energy. He has published many papers on modeling in microeconomics, operations research, and statistics.
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Michael YE teaches economics at St. Mary's College of Maryland. He has experience as a consultant to a wide variety of private and government organizations, including the U.S. Department of Defense and U.S. Department of Energy. He has published many papers on modeling in microeconomics, operations research, and statistics.
John ZYREN joined the Energy Information Agency at the U.S. Department of Energy as a senior industry economist after working as a private consultant in the energy industry. His principal areas of research are in the quantitative modeling of crude oil and petroleum product price behavior.
Joanne SHORE has spent over 25 years analyzing and modeling energy markets. She began her career in the nuclear industry, but later joined Gulf Oil's corporate planning department where she performed studies in areas such as downstream profitability and the implications of economic, political, and social changes on the oil business. Ms. Shore then spent 15 years in private consulting, focusing on analyses of crude oil, gasoline, distillate, and propane markets to explain price movements and to determine the impacts of changing regulations. In 2000, she joined the Energy Information Administration's Petroleum Division as lead operations research analysis team leader.