There were a few occasions where demand for design services decreased on a month-to-month basis in 2015, but the Architecture Billings Index (ABI) finished the year in positive territory, as it did in eight of the 12 months of the year, according to the American Institute of Architects.

As a leading economic indicator of construction activity, the ABI reflects the approximate nine- to 12-month lead-time between architecture billings and construction spending.

The AIA reported the December ABI score was 50.9, up from the mark of 49.3 in the previous month. This score reflects a slight increase in design services (any score above 50 indicates an increase in billings). The new projects inquiry index was 60.2, up from a reading of 58.6 the previous month.

“As has been the case for the past several years, there continues to be a mix of business conditions that architecture firms are experiencing,” said AIA Chief Economist Kermit Baker. “Overall, however, ABI scores for 2015 averaged just below the strong showing in 2014, which points to another healthy year for construction this year.”

Key December ABI highlights:

• Regional averages: West (53.7), South (53.3), Northeast (46.7), Midwest (46.1)
• Sector index breakdown: multifamily residential (52.9), institutional (52.2), commercial / industrial (47.3), mixed practice (46.5)
• Project inquiries index: 60.2
• Design contracts index: 51.0.