According to a study commissioned by the Man Booker Prize, Ferrante’s My Brilliant Friend was the #1 bestselling translated literary fiction book in the UK in 2015.

Last year, Sal Robinson wrote that the question whether translated literature sells is too large to ever be answered simply. In response to a slew of trend pieces claiming that the success of writers like Karl Ove Knausgård and Thomas Piketty was spurring a demand for translated books, Robinson wrote: “it seems necessary to state the obvious, just so that the conversation can move on. And that is that books in translation do sell, and at bestseller levels (which is often the focus of such trend pieces). They’ve been selling for years.”

The point is that it’s easy for the casual observer to jump to conclusions about the state of fiction in translation when a particular author becomes hot, or even when a sales data indicate a shift, as they do in a new report commissioned by the Man Booker International Prize that looks at sales of translated fiction published in the UK between 2001 and 2015.

As Nikki Griffiths wrote on MobyLives last week, the study, which was conducted for the Booker Foundation by Nielsen Book, shows the translated fiction market “punching beyond its weight.” Citing numbers from a press release on the Man Booker Prize website, she explains: “While in the UK the physical fiction market is generally on the slide, falling from 51.6 million copies sold in 2001 to 49.7 million in 2015, translated fiction has risen from 1.3 million copies to 2.5 million.”

The growth is indeed significant, and it seems especially so in a line from the press release claiming that, on average, “translated fiction books sell better than books originally written in English, particularly in literary fiction”—a statement that may be true, but should be considered alongside the fact that translated fiction makes up only 1.5% of fiction, and 3.5% of literary fiction published in the UK.

The Man Booker study also looked at translated books’ source languages, showing that sales of fiction translated from the French doubled in the 14-year period, while sales of Italian literary fiction rose from 37,000 in 2001 to 237,000 in 2015, “due in no small part to the Ferrante phenomenon.” Indeed, Robinson’s point about the success of translated authors on the bestseller level seems to apply here. It’s also worth noting that sales of South Korean fiction are up, which the report describes as “a reflection of the South Korea market focus at London Book Fair” (the 2016 Man Booker Prize has just gone to the South Korean writer Han Kang for her arguably Kafkaesque novel The Vegetarian).

All of this is to say that making large claims about how successful translated fiction is, even in one country, is a tricky business. Draw conclusions at your own risk.