Oil is up about 17% since OPEC announced that it had agreed to cut output on November 30. That deal was expanded to include important non-OPEC producers on December 10.

Is that enough, though, to switch oil supply from surplus to deficit and to cut into global oil inventories?

The International Energy Agency says “Yes, if….”

Global oil stockpiles will fall by about 600,000 barrels a day in the next six months, the IEA forecasts. That’s six months earlier than the agency had forecast for supply to move to a deficit.

But the forecast came with a big “if.” “If OPEC promptly and fully sticks to its production target” and other producers cut as agreed, “the market is likely to move into deficit in the first half of 2017,” the IEA said in its monthly report.

I’d add my own “if” to that of the IEA. A great deal depends on what level OPEC decides it has agreed to cut from. The agreement doesn’t go into effect until January but in November OPEC pumped a record 34.2 million barrels a day.”

Looking at the December 10 deal, the agency reduced its 2017 estimate for total non-OPEC supply by 220,000 growth to just half of its earlier estimate. That projection assumes that Russia will cut its output to 11.3 million barrels a day in the second quarter from an estimated 11.6 million barrels in the fourth quarter.

The agency also increased its projections for global oil demand in 2017 by 100,000 barrels a day. Consumption will rise by 1.3 million barrels a day, or 1.4%, to 97.6 million barrels a day.

U.S. benchmark West Texas Intermediate finished today at $52.29, down 1.3%, and international benchmark Brent closed at $55.72, ahead 0.05%.