Everyone is looking for someone to blame for high prices of oil and other mineral and agricultural commodities. Speculators (among others) are high on the list, followed by the Federal Reserve. While I don’t think blame is necessarily the right concept here, I have been arguing that low real interest rates have worked to raise real commodity prices through a number of channels. Each of these channels could be called “speculation,” if speculation is defined as behavior based on expectations of future prices.

A number of commentators, including Don Kohn and Paul Krugman, have argued that low interest rates and speculation cannot be the sources of the problem, because oil inventories are low. It is true that low interest rates, other things equal, should in theory increase firms’ desire to hold inventories.

US crude oil inventories do not appear to be especially low in the graph above, showing June 1998-June 2008 (from Bloomberg). But it is true that they are not especially high either.

We are talking about relatively integrated world markets, however, so it is world inventories that should matter most. According to the International Energy Agency’s Oil Market Report, oil inventories held in developed countries have been above average during most of the last year, as the next graph shows. They rose sharply in January 2008, which happens to be the month when the very aggressive cuts in US interest rates took place. These numbers are far from conclusive, but still…

The theory is meant to explain the mystery why prices of virtually all mineral and agricultural prices are high, not just oil, and in some ways fits others better. Inventories of some commodities are indeed high now. The price of gold, the last graph shown, is a good example. Here the evidence supports the theory (1) that easy monetary policy has driven up the price, and (2) that one channel is low interest rates making it more attractive to stockpile the yellow metal. But, as with oil, the biggest inventory is the one underground.

[Thanks to Pravin Chandrasekaran.]

Dear readers: If you wish to comment on this post, please go to:
http://www.rgemonitor.com/us-monitor/252799
or http://www.rgemonitor.com/us-monitor/bio/660/jeffrey_frankel .
I am turning off the comment function on my own site, because I am tired of sorting through 35 spam posts on my blog every night.

Fed Vice Chairman Donald L. Kohn in a speech yesterday, addressed a theory to which I am partial: the theory that low real interest rates have been a factor behind the continued rise in prices of agricultural and mineral commodities, including oil, over the last year.

The relevant excerpt: “Some observers have questioned whether the news on fundamentals affecting supply and demand in commodities markets has been sufficient to justify the sharp price increases in recent months. Some of these commentators have cited the actions of the Federal Reserve in reducing interest rates as an important consideration boosting commodity prices. To be sure, commodity prices did rise as interest rates fell. However, for many commodities, inventories have fallen to all-time lows, a development that casts doubt on the premise that speculative demand boosted by low interest rates has pushed prices above levels that would be consistent with the fundamentals of supply and demand. As interest rates in the United States fell relative to those abroad, the dollar declined, which could have boosted the prices of commodities commonly priced in dollars by reducing their cost in terms of other currencies, hence raising the amount demanded by people using those currencies. But the prices of commodities have risen substantially in terms of all currencies, not just the dollar. In sum, lower interest rates and the reduced foreign exchange value of the dollar may have played a role in the rise in the prices of oil and other commodities, but it probably has been a small one.” (Speech at the National Conference on Public Employee Retirement Systems, New Orleans, Louisiana, May 20, 2008).

As real interest rates have come down over the last year, real commodity prices have accelerated upward despite declining economic growth. (See graph, where the commodity price has been inverted so that one can see the correlation visually.)

The effect of interest rates can be demonstrated both theoretically and empirically. I have argued that the effect can come through any of three channels: inventories, production, and financial speculation.

Historically, real interest rates have had an inverse effect on oil inventories (when controlling econometrically for three other relevant factors). Nevertheless, I have to admit that inventory levels have not over the last year risen in a way that would support the theory. I thus have to rely more on the other channels of transmission to explain recent developments.

Stocks of oil held in deposits underground dwarf those held in inventories above-ground, and the decision how much to produce is subject to the same calculations trading off interest rates against expected future appreciation as apply to inventories. (The classic reference is Hotelling’s Rule.)

Apparently the Saudis have indeed deliberately decided to leave theirs in the ground. “King Abdullah, the country’s ruler, put it more bluntly: “I keep no secret from you that, when there were some new finds, I told them, ‘No, leave it in the ground, with grace from God, our children need it’.’’ FT 5/19/08. I see the interest rate as part of the Saudis’ decision how much oil to pump. Because the current rate of return on financial assets is abnormally low, they can do better by saving the oil for the future than by selling it today and investing the proceeds. Holding back production raises today’s oil price, to a point where the expected future return on oil has fallen to the same level as the interest rate. Hence the inverse effect of real interest rates on real oil prices. The same logic governs others’ decisions regarding how much copper to mine, how much forest to log, etc.

In addition to the link from world real interest rates to world real commodity prices, there is the less novel link from individual countries’ real interest rates to commodity prices expressed in their own currencies, a link that primarily passes through their exchange rates. For almost all of the eight floating-rate countries that I tested, both the US real interest rate and the local real interest rate (as a differential relative to the US rate) simultaneously had significant effects on real commodity prices. The effect is equally applicable to the United States: When the Fed eases and the dollar depreciates, the price of oil in dollars goes up quickly. This despite what many have thought in the past, that there is little effect because oil is invoiced in dollars.

If strong economic growth is not the explanation for the large increases since 2001 in prices of virtually all mineral and agricultural commodities, then what is? One wouldn’t want to try to reduce commodity markets to a single factor, nor to claim proof of any theory by a single data point. Nevertheless, the developments of the last six months provided added support for a theory I have long favored: real interest rates are an important determinant of real commodity prices. High interest rates reduce the demand for storable commodities, or increase the supply, through a variety of channels:

• by increasing the incentive for extraction today rather than tomorrow (think of the rates at which oil is pumped, copper 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 spot commodity contracts (think gold), and into treasury bills.

All three mechanisms work to reduce the 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 the 1970s, and again during 2001-2004. It’s the original “carry trade.”

The theoretical model can be summarized as follows:

A monetary expansion temporarily lowers the real interest rate (whether via a fall in the nominal interest rate, a rise in expected inflation, or both – as now). Real commodity prices rise. How far? Until commodities are widely considered “overvalued” — so overvalued that there is an expectation of future depreciation (together with the other costs of carrying inventories: storage costs plus any risk premium) that is sufficient to offset the lower interest rate (and other advantages of holding inventories, namely the “convenience yield”). Only then do firms feel they have high enough inventories despite the low 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.There was already some empirical evidence to support the theory: Monetary policy news and real interest rates, along with other factors, do appear to be significant determinants of real commodity prices historically. (For a simpler illustration, see graph below).

But the events since August 2007 provide a further data point. As economic growth has slowed sharply, both in the US and globally, the Fed has reduced interest rates, both nominal and real. Firms and investors have responded by shifting into commodities, not out. This is why commodity prices have resumed their upward march over the last six months, rather than reversing it.