The Architecture Billings Index, an indicator of U.S. non-residential building activity, rose in December, the American Institute of Architects (AIA) said on Wednesday.

The index rose to 52.2 in December from 50.9 in November, making it ten months that the index had risen in 2014. A reading above 50 indicates an increase in billings. “Particularly encouraging is the continued solid upturn in design activity at institutional firms, since public sector  facilities were the last…