Oil prices have had a good run since bottoming out last June: up more than 40%. How could this be for a staple commodity? The answer is, of course, financial investors’ gate-crashing the normal working of supply and demand. These investors reckon there is a negative correlation between the number of operating US rigs (as reported by Baker Hughes) and the price of West Texas Intermediate Crude. (WTI prices generally but not uniformly move with higher grade Brent). As is often the case, Figure 7 does not put beyond doubt which is the chicken and which the egg but it seems clear that the higher the price the more rigs are operating. Apparently, shale oil rigs are relatively easy to make operational and the question arises as to whether US shale represents sufficient ‘swing’ capacity to prevent OPEC and their new partner Russia from taking prices as high as they would like. Probably not completely, for logistical and long-term contractual reasons, but enough to place some sort of ceiling. Enter the traders who can see a range of (say) $45-70, wide enough to make them eager to join a rather scary ménage à trois and prevent a settled price equilibrium.