Cumulative percentage change in the Brent oil price since June 19, 2014, based on 200 commodity price co-Movements

Source: Bank of England November 2015 Inflation Report

The BOE bases this analysis on the co-movement of oil prices with those of other commodities. If oil prices drop simultaneously with other commodity prices, then presumably some common cause is the source. The supply of a range of commodities is unlikely to balloon all at the same time. Therefore, if supply is not the cause, then weak demand is likely to blame.

The BOE cited weaker growth in countries such as China among the reasons for weak demand. (The Paris attacks, as grave as they were, have no immediate, direct and material implications for the oil supply. Syria itself is a minor supplier, and bombing of ISIS in Iraq and Syria are not new, even if their intensity and scope is likely to increase.)