In the Association of American Publishers' first report on industry sales for 2016, the organization found that total revenue fell 6.6% in the year, compared to 2015.

Based on sales from 1,207 companies that report to AAP’s StatShot program, total revenue last year hit $14.25 billion, down from $15.26 billion in 2015. Later this year, AAP will release estimates for industry sales that include results from publishers that do not report to StatShot.

Only two of the eight major publishing categories posted increases in the year. The strongest increase came from the relatively small religious presses category, where sales rose 8.4%. The children’s/young adult category had a 3.7% gain in 2016, with revenue rising to $1.78 billion.

The worst financial performance came in the professional books segment, where sales dropped 20.8%. Sales of higher education materials fell 13.4% in the year, while sales of K-12 instructional materials down 9.0%.

The adult trade book segment, which is the largest in the industry, showed a 2.3% decline in sales, with revenue dropping from $4.96 billion in 2015, to $4.85 billion last year. Within adult trade, sales of e-books from reporting publishers fell 13.9%, to $$12.021 billion. Hardcover sales fell 3.7%, to $$1.51 billion. Downloadable audio had the strongest gain in the year, with sales up 24.9%, to $254.9 million. Trade paperback had the highest sales among adult trade formatswithin adult books, as sales rose 5.3%, to $1.57 billion.