Oil prices have retreated approximately $4.70 since the beginning of March and about $5.50 since their year-to-date high in early January. The decline comes on the heels of a brief period of stability in the fourth quarter of 2016 after OPEC members reached a production agreement to reduce inventories and promote prices higher.

As prices inched higher and showed stability, U.S. producers ramped up production and ultimately inventories. U.S. shale production had its largest month-over-month increase, 1.7%, since Bloomberg began tracking the data in May 2015. U.S. oil rig count as of Dec. 31 was up 67% since hitting a historic low in May, and 25% since the end of September.

OPEC has stuck to its production limits, at least through the end of February. The cartel is by far the largest producer, but concerns grew throughout 2016 about its ability to weather lower prices for the long term.