The monthly Architecture Billings Index (ABI) came in at a score of 54.3 in March, up 3.6 points from February's 50.7, the AIA announced today.

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, and regionally, as well as by project type. A score above 50 represents an increase in billings from the previous month, while a score below 50, as seen in January, represents a contraction.

Architecture billings rebounded in February after a disappointing reading one month prior, which came in the wake of December's impressive 55.6 reading—a nine-year high. The new project inquiries index— the most reliable indicator of future billings—declined slightly to a score of 59.8 in March, indicating billings might ease in April.

“The first quarter started out on uneasy footing, but fortunately ended on an upswing entering the traditionally busy spring season,” said AIA chief economist Kermit Baker, Hon. AIA, in a press release. “All sectors showed growth except for the commercial/industrial market, which, for the first time in over a year displayed a decrease in design services.”

After five consecutive months of growth, the design contract portion of the index decreased 2.4 points in March, from February's score of 54.7, to a score of 52.3.

Regional billings, which, unlike the national score, are calculated as a three-month moving average, increased in all four regions during March, after declines in February. The Midwest experienced the biggest rebound, growing 1.2 points to 54.6 from February's reading of 53.4. The West was close behind, rising 1.1 points from February's reading of 49.1, to 50.2. Billings increased marginally in the Northeast and the South, growing 0.6 points and 0.9 points, respectively, to scores of 52.4 and 52.6.

Architecture billings in the mixed-use, institutional, and commercial/industrial sector also rebounded from February's reading, posting scores of 53.7, 52.9, and 49.8, respectively. Billings rebounded most in the residential sector in March, increasing 3.5 points to 54.6, from February's reading of 51.1. (Results of the sectors and regions are calculated as a moving average of the past three months.)