Billings to architectural firms continued to hover in positive territory in June, but activity in the Midwest trailed other regions of the country, the American Institute of Architects (AIA) said today. The AIA reported a score of 51.6, down from a mark of 52.9 in May. The billings index for the Midwest was 48.3 Any reading above 50 reflects an increase in demand for design services. An index of inquiries for new projects stood at 62.6, up from 59.1 in May. The billings index reflects the nine- to 12-month lag time between architecture billings and construction spending. "The construction sector seems to be stabilizing, particularly in the nonresidential categories," Jessica Reinert, AIA Iowa executive director, said in a news release. "However, threats such as construction costs, labor availability and inability to find financing for real estate projects still remain an issue for the industry to reach a sustained recovery."