Audiobooks began generating significant revenue for authors in the mid-2000s as online booksellers such as Amazon developed infrastructure to deliver digital audiobooks to listeners through downloadable files. With the advent of smart phones and mobile apps, audiobook use has become even easier, driving sales even higher. The audiobook market has grown steadily with total audiobook sales reaching almost $1 billion in 2018 and rising to $1.6 billion in 2022. With sales of audiobooks projected to continue increasing, additional revenue streams like this may soon become a far more significant source of income for many authors than in the past. Data Source statista.com: Audiobook sales revenue in the United States from 2018 to 2021