Building products maker USG Corp. reported a smaller fourth-quarter loss than it had a year ago and said it thinks the worst of the economic downturn is behind the company.

The Chicago-based company, the largest U.S. distributor of drywall, on Wednesday said it lost $121 million, or $1.17 a share in the fourth quarter. That compares with a year-ago quarterly loss of $598 million, or $6.02 a share.

For the full year, the net loss totaled $405 million, or $4.03 a share, compared with $787 million, or $7.93 a share, in 2009.

“While 2011 is likely to be another difficult year, we think the worst may be behind us,” said James Metcalf, USG’s president and CEO. “There is still a high degree of uncertainty about the shape and timing of the recovery, but we know that our operating strategies are working and that the fundamentals underlying our core businesses are solid.”