Billings at architecture firms accelerated to their strongest pace of growth since December 2010. As a leading economic indicator of construction activity, the Architecture Billings Index reflects the approximate nine to 12 month lag time between architecture billings and construction spending. The American Institute of Architects reported the October ABI score was 52.8, up from the mark of 51.6 in September. This score reflects an increase in demand for design services (any score above 50 indicates an increase in billings). The new projects inquiry index was 59.4, compared to a mark of 57.3 the previous month.