The Architecture Billings Index (ABI) has fallen into negative terrain after five months of positive readings. The score sat at 48.4 for April, down from 50.4 in March. The new projects inquiry index was 54.4, down from 56.6 the previous month.The billings index, a leading economic indicator of construction activity, reflects the approximate lag of nine to 12 months between architecture billings and construction spending.

“Considering the continued volatility in the overall economy, this decline in demand for design services isn’t terribly surprising,” said AIA Chief Economist Kermit Baker. “Also, favorable conditions during the winter months may have accelerated design billings, producing a pause in projects that have moved ahead faster than expected.”

The West had the lowest reading at 48, the Northeast toped the list at 51, and the Midwest and South came in second and third with 50.1 and 49, respectively.

Scores above 50 indicate an aggregate increase in billings, and scores below 50 suggest a decline. The regional and sector categories are calculated as a three-month moving average, whereas the index and inquiries are monthly numbers. Results are seasonally adjusted to allow for comparison to prior months.