Architects in the Midwest reported an increase in requests for design services in December, leading all regions of the country, the American Institute of Architects (AIA) said.

"We are anticipating the advancements in firm billings that we saw at the end of 2012 continue through 2013 in the Midwest, especially Iowa." Jessica Reinert, executive director of the AIA's Iowa chapter, said in a news release.  

The organization's overall index of billings declined to 52 December from 53.2 in November. However, firms in the Midwest had an increase to 55.7 from 55.1 the previous month. Any reading above 50 reflects an increase in activity.

Because of a typical nine- to 12-month gap between billings and spending, the index is considered an indicator of future construction activity.

Designs for commercial and industrial projects led the way in requests for design services.