A major survey of American authors has uncovered a crash in author earnings described as “a crisis of epic proportions” – particularly for full-time literary writers, who are “on the verge of extinction”.

Surveying its membership and that of 14 other writers’ organisations in what it said was the largest survey of US authors’ earnings ever conducted, the Authors Guild reported that the median income from writing-related work fell to a historic low in 2017 at $6,080 (£4,760), down 42% from 2009.

Writers of literary fiction are particularly affected, said the Authors Guild, with those authors experiencing the biggest recent decline in writing-related earnings – down 43% since 2013. Isolating book-related income, the decline was even steeper, down to $3,100 in 2017 – more than 50% down on 2009’s median of $6,250. In total, 5,027 authors provided detailed responses to the survey.

The Authors Guild said the reduction in earnings for literary writers “raises serious concerns about the future of American literature – books that not only teach, inspire and elicit empathy in readers, but help define who Americans are and how the US is perceived by the world”.

“When you impoverish a nation’s authors, you impoverish its readers,” said Authors Guild president James Gleick. Vice-president Richard Russo added that “there was a time in America, not so very long ago, that dedicated, talented fiction and non-fiction writers who put in the time and learned the craft could make a living doing what they did best, while contributing enormously to American knowledge, culture and the arts. That is no longer the case for most authors, especially those trying to start careers.”

Author TJ Stiles said: “Poverty is a form of censorship. That’s because creation costs. Writing requires resources, and it imposes opportunity costs. Limiting writing to the financially independent … punishes authors based on their lack of wealth and income.”

The survey found that even those who consider themselves to be full-time writers are forced to hold down multiple jobs to earn enough money to survive. Just 21% of full-time published authors derived 100% of their income from their books in 2017, with the need to focus on other avenues for income meaning that literary authors are writing and publishing books less often.

“It takes writers longer to research and write books, since they have to do it between other money-earning ventures,” said the Guild, describing the situation as “a crisis of epic proportions”.

“The quality of books written by authors holding down other jobs may be affected since their attention is divided and writing is often pushed to what spare free time is left,” it added.

The one bright point in the survey was for self-published writers, who were the only group to experience a significant increase in earnings – up 95% in book-related income between 2013 and 2017, with the number of authors self-publishing up by 72% since 2013. But the Guild pointed out that self-published authors still earned 58% less than traditionally published peers in 2017.

The Authors Guild blamed the crisis on the “growing dominance of Amazon”, which it said forced publishers to accept narrower margins and then pass their losses on to authors, as well as publishers’ focus on blockbuster writers at the expense of lesser-known names, as well as a 25% royalty rate for ebooks.

“Amazon, but also Google, Facebook and every other company getting into the content business, devalue what we produce to lower their costs for content distribution, and then take an unfair share of the profits from what remains for delivering that reduced product,” said Russo. “We get that they like to move fast and break things, but it’s no longer in their own interest to break us. If even the most talented of authors can no longer afford to write, to create, who’s going to provide the content?”

The survey follows similar research conducted in the UK in 2018, which found that median earnings for professional writers had fallen by 42% since 2005 to under £10,500 – well below the minimum wage of £15,269.