While you were pinning feminist Harry Potter slogans to your vision board or listening to Hermione's stellar Lemonade remix , a Tumblr fan theory has been circulating to explain the curiously small class sizes at the universe's preeminent school for witchcraft and wizardry. BuzzFeed found an old J.K. Rowling interview from 2000 in which the author explained that Hogwarts has about 1,000 students. But the math — both in the books and on screen — doesn't seem to hold up. A thousand students divided between the school's seven grades and divided again among the four houses means that there should have been about 35 students in Harry's matriculating Gryffindor class. But screenshots from the tour Percy Weasley gives the first year students in the Sorcerer's Stone movie only show about half that amount.A Tumblr user has come up with the most tragic fan theory to explain the inconsistency. "It’s actually entirely possible that there was a baby drought for a few years in the wizarding world," marauders4evr wrote, "leading to a smaller class size a decade later."The fan's theory matches the statistical rise in births following major conflicts, both in the wizarding world and in our real one. A 2009 study in the journal Evolutionary Biology even suggested that the post-conflict surge in births usually results in more male offspring.Read the fan's full theory, below.