Led by a 34% increase in sales of digital audio, sales of audiobooks rose 20% in 2015 over 2014, to an estimated $1.78 billion, according to the Audio Publishers Association's annual survey of industry trends. The report also found that units increased 24%.

As sales have increased, audio publishers have upped the title output to meet demand. The APA said that the number of titles released by the 20 companies that take part in the survey hit 35,574, a 37%increase over 2014. (The sales and unit estimates are also based on actual sales from 20 reporting companies that the research firm, Management Practice, extrapolates from to get an estimate for the entire industry.)

Other trends identified in the survey held true to previous years. Sales of adult titles accounted for 90% of overall audiobook sales, and fiction was by far the favorite category, accounting for 76% of revenue. Most consumers, 96%, were found to buy unabridged audiobook titles.