US architecture firms said billings improved for a third straight month in December, indicating construction of buildings including warehouses, offices and shopping centers will rise for most of this year.

The Architecture Billings Index rose to 55.4 last month from 55.3 in November, the Washington-based American Institute of Architects said yesterday in a statement. December's score was the highest since July, when it reached 60. A score above 50 indicates billings increased from the previous month.

December's increase may be the last before developers cut spending on fears of a recession, said Kermit Baker, the institute's chief economist. Falling retail sales, rising unemployment and dropping share prices have led some economists to conclude that the US has already entered a recession. Construction spending typically follows billings by about nine to 12 months.

"I'm a bit surprised by how strong the numbers have been," Baker said in an interview. "Talk about a a recession has changed a great deal in the past three weeks."