This heartbreaking Harry Potter fan theory explains why Hogwarts classes are so small

Ever wondered why there were so few Gryffindors in Harry's year at Hogwarts?

JK Rowling once said there were 1,000 students at the School of Witchcraft and Wizardry, so where are they all? If you divide 1,000 by the number of years (7) and the number of houses (4), there should be about 35 students sorted into Gryffindor when Harry joins. But, instead, there are only around 18. Here's Percy leading them to their common room...

Weird, huh?

Well, one Tumblr user has a heart-breaking – and really rather convincing theory – about why that might be. Prepare to feel a little melancholy...