Unlike much of the rest of the media industry, the world of publishing enjoyed a rise in sales as summer reading season kicked into gear in June. But one of the most successful authors of fiction in publishing history, J.K. Rowling, was an exception to that growth, just as she plunged herself into a firestorm of controversy over transgender identity.

Last month, sales in print books in fiction overall rose 31.4% in the U.S. from May, according to figures from NPD BookScan, with fiction titles in adult, young adult and juvenile sectors all seeing similar double-digit growth. The author of the “Harry Potter” series, by contrast, saw her print book sales in the U.S. rise just 10.9% in June. “Harry Potter” sales — including licensed titles not authored by Rowling — rose even less, just 7.7% for the month. While the BookScan figures do not account for other points of sale — like eBooks, sales to libraries and direct publisher sales — they do point to a remarkably sudden and sharp drop in print sales for Rowling’s books.

The lagging returns for Rowling are especially significant considering that in 2019, her print book sales in June rose right alongside sales for the rest of the industry: 35.2% for the author compared with 33.3% for fiction overall, according to NPD BookScan. (Rowling did release four new “Harry Potter” titles in 2019 connected to the “History of Magic” audiobook, but they were eBook versions only, and the first two titles debuted on June 27, so they don’t factor into these sales figures.)

“Looking at [Rowling’s] performance against the rest of the market, especially as benchmarked against her performance in 2019 — which was very consistent with the rest of the market — I think she’s down,” says Kristen McLean, analyst and executive director of business development at the NPD Group. “She’s certainly underperforming the rest of the market, comparatively, by two thirds.”

Rowling’s slowing sales in June also aren’t consistent with her print sales for the rest of the year, which are up 26.5% compared to the first half of 2019. McLean points to a general upswing in the juvenile title sector starting in March — at first, in non-fiction — as parents scrambled to come up with productive ways to occupy their children’s time as schools shut down in the wake of the pandemic.

But then in June, Rowling’s sales straggled, while the rest of the industry surged forward. Had the “Harry Potter” titles risen at the same rate as the overall juvenile sector in June, they could have earned as much as $2 million more in total sales, according to NPD BookScan data. Similarly, had Rowling’s sales followed the overall fiction market, her books could’ve earned upwards of $1.7 million more in total sales.

McLean declined to speculate on why, citing a lack of consumer research. But it’s hard to ignore that, since the first week of June, Rowling has incurred widespread criticism after she began repeatedly expressing contentious views on transgender identity.

“Harry Potter” film stars Daniel Radcliffe, Emma Watson and Rupert Grint, “Fantastic Beasts” star Eddie Redmayne, “Harry Potter” and “Fantastic Beasts” screenwriter Steve Kloves, and “Harry Potter” fansites The Leaky Cauldron and MuggleNet have all publicly rebuked Rowling for her stances on trans people. After GLAAD issued a statement calling on all organizations affiliated with Rowling to publicly denounce Rowling’s views, Warner Bros. (which releases the “Harry Potter” and “Fantastic Beasts” films) and Universal Parks (which is home to the Wizarding World of Harry Potter theme parks) also issued statements in support of diversity and inclusion — though studiously avoiding using the words “transgender” or “J.K. Rowling.”

The controversy erupted after Rowling posted a series of tweets on June 6 contending that women can only be identified by their biological sex. Over the ensuing six weeks, Rowling has repeatedly revisited the issue of transgender identity, from a lengthy essay Rowling posted to her personal website on June 10 in which she evoked her past history with sexual assault to assert her support for “single-sex spaces.” On July 5, she insisted that prescribing hormones to transgender children is akin to “a new kind of conversion therapy”; two days later, Harper’s published an open letter signed by Rowling and several other literary and media figures condemning public shaming. That letter was widely interpreted to be at least in part in reaction to trans activists aggressively pushing back against anyone who denies transgender identity.

A spokesperson for Rowling’s U.S. publishers did not immediately respond to a request seeking comment on her book sales.