"Considerable uncertainties" surrounded the U.S. economic outlook, particularly the drag on exports from slowing global growth, low investment caused by the decline in oil prices and a “disappointing” recent drop in U.S. job growth.

The probability that the world's biggest economy will enter a recession in the next 12 months jumped to 15 percent, its highest level since October 2013, according to economists surveyed Oct. 2-7 by Bloomberg. The median had held at 10 percent for 13 consecutive months.

A barrel of crude oil costs under $50, having more than halved in price since June. This means wells are pumping out smaller profits, if not losses. When oil prices plunge and billions of dollars are at stake, oil companies tend to respond quickly to curb production. The number of active rigs has fallen 50 percent since October, according to Baker Hughes, the oilfield services company. This has led to layoffs, tighter budgets and fewer orders for equipment, all which hurt growth.

OPEC: The oil market outlook in 2015

EIA: Fuel economy improvements show diminishing returns in fuel savings

OPEC published Monthly Oil Market Report July 2014

GLOBAL ECONOMY WEEK AHEAD-Jobs, cars seen cementing U.S. spring rebound

IEA, International Energy Agency published March Oil Market Report

OPEC published Monthly Oil Market Report