"The complexity of the oil pricing arrangements makes it difficult to demonstrate convincingly that benchmark oil prices fully reflect physical supply and demand conditions rather than the actions of uninformed financial speculators. Nevertheless, movements over time in the price differentials for the various benchmark crudes are broadly consistent with changes in demand and supply. The Brent-WTI spread provides a good example of the influence of such factors on oil price differentials. Prior to 2011, Brent and WTI prices generally moved in tandem, with the spread largely reflecting the costs of transporting Brent-referenced crude oils to the United States. In recent years, however, increased volumes of crude oil from North Dakota and Canada have flowed into Cushing, leading to a build-up in inventories. Most pipelines flow from the rest of North America into Cushing, making it difficult to move the extra crude oil out of Cushing. This has led to persistent inventory bottlenecks, which have weighed heavily on the price of WTI over the past 18 months, leading the Brent-WTI spread to widen to US$10–30 per barrel. The recent widening of the Brent-WTI spread is also likely to reflect concerns about declining production volumes in the North Sea."
Eine Studie von Stephanie Dunn und James Holloway über den komplexen Ablauf der Rohölmärkte, die Preisbildung und den Spread der Benchmarks Brent & WTI. Erschienen im Quarter Bulletin der Reserve Bank of Australia, Sydney (September 2012).