The AIA's monthly Architecture Billings Index (ABI) came in at a score of 50.4 in December, a 4.3-point drop from the previous month, but marking the 15th consecutive month of gains. The ABI is a leading economic indicator of construction activity in the U.S., and reflects a nine- to 12-month lead time between architecture billings and construction spending nationally, regionally, and by project type. A score above 50, as seen in December, represents an increase in billings from the previous month, while a score below 50 represents a contraction.

“Given the concerns over the ongoing tariff situation, it is not surprising to see a bit of a slowdown in progress on current projects,” said AIA chief economist Kermit Baker, Hon. AIA, in a press release. “Growing anxiety over unstable business conditions and the partial shutdown of the government may lead to further softening in the coming months.”

In December, design contracts posted a score of 52.1—a 2.5-point decrease from November's score of 54.6. Design contracts continue to come in above the 50-point threshold—as they have every month over the past year—a sign that momentum is strong, despite slow growth and month-to-month fluctuations.

The scores for regional billings—which, unlike the national score, are calculated as three-month moving averages—increased in two regions in December. The billings score for the Midwest grew 3.2 points to a score of 56.3. Demand for design services in the West increased slightly by 0.2 points to a score of 49.2. Billings decreased in the South by 1.1 points, to a score of 49.4, and demand for design services decreased significantly by 5.2 points to a score of 51.6 in the Northeast.

Billings decreased in three of the four individual industry sectors in December. The multifamily residential score dropped by 1.4 point to a score of 49.8, the mixed practice sector's score decreased by 3.6 points to a score of 50.2, and the commercial/industrial sector's score decreased by 2.6 points to a score of 51.2 The Institutional sector posted a score of 53.1, a 2.3-point increase from November's score of 50.8. (Results of sectors are also calculated as three-month moving averages.)