Architects participating in the American Institute of Architects (AIA) work on the Boards survey said their billings took a dramatic downward turn in February as the Architecture Billings Index (ABI) fell to 41.8, the lowest score since the immediate aftermath of Sept. 11 in October 2001.

The ABI has now fallen more than 13 points since December, the largest two-month drop ever recorded in the dozen years of the index.

This drop serves as the clearest indicator yet that softer business conditions are coming. Inquiries growth continued to slow this month, as the score fell to 54.3. Although any ABI score above 50 indicates growth, this is the lowest indication of inquiries growth in more than five years.

All regions of the country, with the exception of the Northeast, reported significantly weaker business conditions in February.

There was a dramatic slowdown at firms with commercial/industrial specializations — from 54 in January to a current score of 40.6.