Audiobooks continued their meteoric rise in 2017, a new report issued by the Audio Publishers Association found, with another year of double-digit growth for both audiobook sales and title output.

Total sales rose 22.7% in 2017, to an estimated $2.5 billion, over an estimated $2.1 billion in sales in 2016. Unit sales rose an estimated 21.5%, the APA reported. Sales are based on reports from about 20 audiobook publishers. The APA then extrapolates from those figures, to derive an estimate for the entire market.

The audience for audiobooks remains young, with 54% of audiobook listeners under the age of 45. They are also consistent readers in all formats, the studies found: not only do audiobook listeners listen to an average of 15 books a year, but 83% of frequent listeners also read a hardcover or paperback over the last 12 months, and 79% also read an e-book.

Listening to audiobooks on smartphones continued to grow in 2017 as well; 73% of listeners used a smartphone to listen to audiobooks at some point in the year, and 47% of listeners chose a smartphone as their listening device on a regular basis, up from 29% in 2017 and 22% in 2015. In terms of genre, the most popular were mysteries/thrillers/suspense, science fiction, and romance.

Libraries remain major drivers for audiobook consumption as well. 52% of listeners said borrowing from a library or library website was instrumental to their listening habit, 43% said they downloaded an audiobook from a library, and 14% said they most often use the library for their digital listening.

Data for the APA's findings is sourced from two surveys—one conducted by independent research firm Management Practice, which polls publishers of audiobooks, and the other the latest consumer study conducted by Edison Research.

“This year’s study confirmed that not only are audiobooks widely perceived as a way to bring more books into people’s days, but they also have a strong association as a means to relax and unwind that is distinct to other forms of spoken word audio,” Tom Webster, senior v-p of Edison Research, said in a statement.

“In addition to the continued stellar sales growth, the results show that our customers are finding more opportunities to listen," Chris Lynch, co-chair of the APA's research committee and president and publisher of Simon & Schuster Audio, said in a statement. "Our heaviest users are book lovers in all formats, and their increased use of audiobooks is allowing them to get through more books, more quickly.”