Streetwise Professor

May 25, 2017

OPEC and Inventories: An Exercise in Game Theoretic Futility

Filed under: Commodities,Economics,Energy — The Professor @ 11:37 am

OPEC met today, and agreed to extend its output cuts for another nine months. OPEC’s focus is on “rebalancing the market,” that is, on inducing a decline in world oil stocks to a level well below their current inflated value. This is far easier said than done, and indeed may be impossible because of the inability of OPEC to commit to a path of future output. This is because inventory changes result from changes in the temporal supply and demand balance.

In a competitive market, stocks accumulate when there are unexpected increases in supply or declines in demand, and crucially, these shocks are expected to be highly transitory. Similarly, market participants draw down on stocks when there are unexpected declines in supply or increases in demand that are expected to be highly transitory.

The “transitory” part of the story is very important. It makes sense to store when expected future supply is less than current supply, i.e., when future scarcity is greater than current scarcity. It makes sense to draw down on storage when future scarcity is expected to be low relative to today: why carry inventory to a time of greater abundance? Markets move things from where/when they are abundant to where/when they are scarce. Highly persistent shocks to supply and demand don’t affect the temporal balance, and hence to don’t lead to temporal reallocations. Temporary shocks (or shocks to future supply/demand) also change the temporal balance, and lead to inventory changes.

In my empirical work on the copper market (where inventory data is pretty good), I document that a net supply shock with a half-life of about 1 month drives inventory changes. Much more persistent shocks (e.g., those with a half-life of a year) have virtually no impact on inventory.

Inventories can also decline if expected future supply rises, or expected future demand declines. An increase in expected future supply reduces the future value of oil, and makes it less valuable to hold oil today for future use. Or to put it another way, it is desirable to smooth consumption, so if expected future supply (and hence future consumption) goes up, it makes sense to increase consumption today. This can only be done by drawing down on inventory. (Time travel that would allow bringing the abundant future supply back to the present would do the same thing, but alas, that’s impossible.)

OPEC’s desire to cause a drawdown in inventory would therefore require it to commit to a path of output. Further, this path would involve bigger cuts today than in the future in order to cause a temporal imbalance involving an increase in future supply relative to current supply.

But it is unlikely that this commitment could be credible, precisely because of the reason that OPEC gives for fretting about inventories: that they constrain its pricing power. Assume that inventories do drop substantially. According to its own logic, OPEC would feel less constrained about cutting output even further because non-OPEC supplies (in the form of stocks) have declined. Thus, if inventories indeed fall, OPEC’s logic implies that it would cut output further in the future.

But this path is inconsistent with the path that would be necessary to induce the inventory decline in the first place. Indeed, market participants, looking forward to what OPEC would do in the event that stocks were to decline substantially, would choose to hold on to inventories rather than consume them. Meaning that OPEC would fail in its objective of reducing stocks. In the game between OPEC and other market participants, OPEC’s own rhetoric about inventories and supply/demand balance severely undercuts its ability to cause others to consume inventories rather than continue to hold them.

In sum, OPEC is likely to have little if any ability to influence inventories. To influence inventories, it would have to commit to an output path, but that commitment is not subgame perfect/time consistent.

Instead, inventories will be driven by factors outside of OPEC’s control, namely, unexpected transitory changes in supply and demand. But the effect of even those shocks will depend on how market participants believe OPEC will behave when inventories are low. The supply changes will mainly result from shocks to non-OPEC producers (e.g., US shale producers) and to politically unstable OPEC nations like Libya, Nigeria, and Venezuela. Inventory changes may also result from information about the durability of output cut agreements and cheating: a surprise increase in the estimates of future cheating would tend to cause inventories to decline today. Thus, perversely from OPEC’s perspective, its wish of lower inventories may come true only when it is widely believed that OPEC output discipline will soon collapse.

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3 Comments »

  1. I don’t really understand how:

    In a competitive market, stocks accumulate when there are unexpected increases in supply or declines in demand, and crucially, these shocks are expected to be highly transitory. Similarly, market participants draw down on stocks when there are unexpected declines in supply or increases in demand that are expected to be highly transitory.

    Would square with, say the natural gas market, in which large stocks are systematically accumulated in the summer for use in the winter. That’s not an unexpected occurrence in the least.

    Comment by FTR — May 25, 2017 @ 9:41 pm

  2. Good question FTR.

    My hunch is that an expected, persistent event like change in season sets the secular trend for stocks of a particular commodity. Departures from this “trend” are explained by unexpected, transitory events. I read the passage as “In a competitive market, stocks accumulate [relative to their usual levels] …”

    Would be interested in hearing what the Prof has to say about this.

    Comment by Eric — May 26, 2017 @ 3:15 pm

  3. @Prof: Excellent lesson, thanks.

    @Eric: For what it’s worth, I’d say you’re right.

    Comment by Hiberno Frog — June 8, 2017 @ 3:47 am

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