U.S. ethanol stocks have fallen for five weeks in a row.

The U.S. Energy Information Administration says the domestic ethanol supply dropped to an 18-week low at 24.2 million barrels, a decrease of 1.288 million from the prior week, but 909,000 above this time last year.

Part of that is the recent decline in production due to seasonal maintenance, which averaged 965,000 barrels a day last week, down 22,000 from the week before and unchanged from a year ago.

Iowa State University’s Center for Agricultural and Rural Development says operating margins for the average Iowa plant improved significantly.

The Renewable Fuels Association says ethanol exports averaged 180,000 barrels a day, a jump of 102,000 from the previous week.

Net inputs of ethanol purchased by refiners and blenders were fractionally lower, even as the volume of gasoline supplied to the market rose by more than 2%.

The USDA’s updated corn for ethanol use estimate is out Friday, May 10.