After beginning 2017 with a slight decline, the Architecture Billings Index (ABI) has shown three straight months of growth in design revenue at architecture firms.

The American Institute of Architects (AIA) reported the April ABI score was 50.9, down from 54.3 in the previous month. This score still reflects an increase in design services, as any score above 50 indicates an increase in billings. The new projects inquiry index was 60.2, up from a reading of 59.8 the previous month, while the new design contracts index increased from 52.3 to 53.2.

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.

“Probably even better news for the construction outlook is that new project work coming into architecture firms has seen exceptionally strong growth so far this year,” says AIA chief economist Dr. Kermit Baker. “In fact, new project activity has pushed up project backlogs at architecture firm to their highest level since the design market began its recovery earlier this decade.”

Regional ABI averages were as follows: South (55.3), Midwest (53.3), West (50.9) and Northeast (50.7).

Here’s how the index broke down by sector: institutional (54.0), mixed practice (53.4), commercial / industrial (52.4) and multifamily residential (49.9).

The regional and sector categories are calculated as a 3-month moving average, whereas the national index, design contracts and inquiries are monthly numbers.