Improved billings over year-end 2014 and an increased number of inquiries contributed to an optimistic economic outlook for U.S. interior design firms at the end of first quarter, according to the American Society of Interior Designers' (ASID) Interior Design Billings Index (IDBI).

ASID's IDBI registered 57.7 at the end of March, compared to 52.3 in December. New project inquiries registered 58.8 at the end of the first quarter, rising two points over December.

Sole-practitioner firms posted a gain from 48 to 52.6 over the year’s first quarter, but small firms with two to nine employees reported the highest billings at 63.2, according to the index.

Geographically, firms in the West experienced a turnaround, surging from 48.5 to 65 over the quarter. Although they experienced a slight decline, Midwest firms ended at 60.5; firms in the South increased to 57. The Northeast, however, continued its downtrend, falling from a billings score of 44 to 40.

According to the index, it was a positive first quarter for design firms specializing in single-family residential projects. That market sector ended the quarter with a two-point increase to 56, while firms specializing in multi-family projects dropped to 47.

In the commercial sectors, the office, hospitality, entertainment and retail segments registered sub-50 IDBI scores. In the institutional sector, the healthcare and government markets experienced declines but maintained scores above 50. Education dipped to an index score of 33.

Looking forward, the design industry’s six-month business conditions index of 73 suggests continued expansion for the interior design industry. When taken together, the ASID six-month interior design business conditions index, the Conference Board’s expectations index and the Dodge Momentum Index signal that the design and construction industries should achieve increased activity through at least early 2016.

For more information, visit asid.org.