Output from producers outside OPEC has also increased materially, but investment in new producing wells has lagged, limiting growth of production in the near term. Crude oil prices are also being distorted by shortages of capacity to upgrade the higher sulphur content and heavier grades of crude oil.
Over the years, increasing demand for the environmentally desirable lighter grades of oil products has pressed refiners to upgrade the heavier crude oils, which compose more than two-thirds of total world output. But refiners have been only partly successful in that effort, judging from the recent extraordinarily large increase in price spreads between the lighter and heavier crudes.