Once again, the literati are twittering about how books by women are reviewed — or ignored.

The feminist organization VIDA has released its latest annual tally of how many women were covered in “the major literary publications and book reviews.” The study notes progress in some venues but finds persistent preference for men’s books in other literary magazines and journals.

But one indication of significant long-term progress in the treatment of books by women comes today from the National Book Foundation. Look at this graph, which has not been published elsewhere before:

(Courtesy of the National Book Foundation)

In the 1950s, the finalists and winners of National Book Awards were more than 80 percent male. But notice how that percentage has steadily fallen until we reach the current decade — then women pulled slightly ahead. Newspapers and journals may have been ignoring women’s books, but this major national prize was growing more enlightened year by year.

Harold Augenbraum, the executive director of the National Book Foundation, has been leading a major study of the organization’s archives. The broad data indicate what discussions about the gender make-up of each year’s finalists miss. “We took it decade by decade,” he says, “and it shows a persistent increase in the number of women” earning nominations and prizes from the National Book Awards.

What accounts for this steady progress? Future studies might examine the gender make-up of the NBA judging panels, but blank spots in the organization’s records during its early years will make that difficult.

This research is part of a massive program to create individual Web pages for each NBA finalist and winner. “We’ve got about 800 done so far,” Augenbraum says. “We’ll do another 300 this year. Within three or four years, we’ll have all 2,100 done.”

The work has been complicated. The awards were first given in 1950. “Some of the authors are now very obscure,” Augenbraum admits. Program assistant Amy Gall sometimes has to go “to small local libraries to find the original books. She’s even had to call these authors from the ’50s and ’60s and ask them if they have a photo of when they won a National Book Award.”

Augenbraum says he doesn’t know what accounts for the steady progress of women among the finalists and winners of the NBA. But it’s definitely encouraging to see.