Determinants of Commodity Prices

The Effects of Interest Rates on Commodity Prices

"Effects of Speculation and Interest Rates in a “Carry Trade” Model of Commodity Prices," 2014, Journal of International Money and Financevol.42, pp. 88-112.  HKS RWP13-022, 2013.  NBER WP 19463 
Stata fies (data, do & log), thanks to Marco Martinez, June 2013 (excludes proprietary Consensus Economics data).   
Video of session on forecasting commodity pricespresented at Conference on Understanding International Commodity Price Fluctuations (organized by the IMF Research Dept. & the Oxford Centre for the Analysis of Resource Rich Economies, March 2013, Washington, D.C.) 

"Determination of Agricultural and Mineral Commodity Prices," with Andrew Rose, Chapter 1 in Inflation in an Era of Relative Price Shocks  (Reserve Bank of Australia: Sydney), 2010:  pp. 9-51. Data.    HKS RWP 10-038.   

"The Effect of Monetary Policy on Real Commodity Prices"Chapter 7 in Asset Prices and Monetary Policy, John Campbell, ed. (U.Chicago Press), 2008: 291-327.   NBER WP 12713. 

"Commodity Prices, Money Surprises, and Fed Credibility," with Gikas Hardouvelis, 1985, Journal of Money, Credit and Banking 17, no. 4, November, Part I, 427-438.  NBER WP 1121, 1983 Reprinted in J.Frankel, Financial Markets and Monetary Policy, 1995.
 A way of isolating monetary effects on commodity prices is to look at jumps in financial market prices that occur in immediate response to government announcements that change perceptions of monetary policy, as was true of Fed money supply announcements in the early 1980s. Money announcements that caused interest rates to jump up would on average cause commodity prices to fall, and vice versa.

 

The central claim of this research:
  
Real interest rates are an important influence on real prices of oil, minerals, and agricultural commodities.  The argument is summarized briefly in "Monetary Policy and Commodity Prices," Vox, 2008; and "An Explanation for Soaring Commodity Prices,"  Vox, 2008.    

        Other factors matter too of course. One way to control for other factors is to employ measures of convenience yield and risk in the equation that determines inventory holdings.  My recent papers on the subject use those variables, along with inventories, to determine commodity prices:

The mechanisms:                                

High interest rates reduce the price of storable commodities through four channels: 
¤  by increasing the incentive for extraction today rather than tomorrow (think of the rates at which oil is pumped, gold mined, forests logged, or livestock herds culled) 
¤  by decreasing firms' desire to carry inventories (think of oil inventories held in tanks) 
¤  by encouraging speculators to shift out of commodity contracts, and into treasury bills
¤  by appreciating the domestic currency and so reducing the price of internationally traded commodities in domestic terms (even if the price hasn't fallen in terms of foreign currency).

All four mechanisms work to reduce the real market price of commodities, as happened when real interest rates where high in the early 1980s. A decrease in real interest rates has the opposite effect, lowering the cost of carrying inventories, and raising commodity prices, as happened in 2007-08 and 2010-11. 

 

The overshooting theory

The theoretical model can be summarized as follows. A monetary contraction temporarily raises the real interest rate (whether via a rise in the nominal interest rate, a fall in expected inflation, or both). Real commodity prices fall. How far? Until commodities are widely considered "undervalued" -- so undervalued that there is an expectation of future appreciation (together with other advantages of holding inventories, namely the "convenience yield") that is sufficient to offset the higher interest rate (and other costs of carrying inventories: storage costs plus any risk premium). Only then are firms willing to hold the inventories despite the high carrying cost. In the long run, the general price level adjusts to the change in the money supply. As a result, the real money supply, real interest rate, and real commodity price eventually return to where they were.
       The theory is the same as Rudiger Dornbusch's famous theory of exchange rate overshooting, with the price of commodities substituted for the price of foreign exchange.
See: "Expectations and Commodity Price Dynamics: The Ohe Overshooting Model," American Journal of Agricultural Economics 68, no. 2, May 1986, 344-348. Reprinted in Frankel, Financial Markets and Monetary Policy, MIT Press, 1995.
      The deep reason for the overshooting phenomenon is that agricultural and mineral prices adjust rapidly, while most other prices adjust slowly.
See: "Commodity Prices and Money:  Lessons from International Finance,"  American J. of Agricultural Economics 66, no. 5, Dec. 1984, 560-66.
          Of course many other things beyond real interest rates and growth influence commodity prices.  One can try to control for some variables, such as global economic activity and uncertainty, as in the 2010 and 2013 papers.

 

Simple graphs of real commodity price index versus short-term real interest rate. (Earlier versions here.)

Real commodity prices (in $) have been negatively correlated with the real 3-month T-bill rate.

Commodity Prices vs. Interest Rate, Plot

(Thanks to Marco Martinez.)

Commodity Price vs. Interest Rate (1951-2018)

The relationship is statistically significant.  Regression results for 1950-2012 are available in Frankel (2013), as are tests with alternative indices from CRB, Dow Jones, Reuters & Goldman Sachs, thanks to R.A. Marco Martinez del Angel.  All these results are still significant in regression results updated to 2018, Frankel & Martinez (pdf).


     Recent commodity prices.


Other research deals with effects of commodity prices, especially in exporting countries, as opposed to causes.