A Harry Potter fan has a sad but very plausible theory about one of the book series’ most confusing aspects, why was Harry’s Hogwarts class size so small? The theory, posted by Tumblr user marauders4evr is definitely very believable based on what we know about the wizarding world, but it might also bring a tear to your eye.

Harry PotterA fan has a depressing theory as to why Harry’s Hogwarts class was so small.

For those who don’t know, Jk Rowling once stated that there were around 1,000 students at Hogwarts during Harry’s time. Now here comes the math. We also know there were seven years, which means there should be about 143 students per year.

Hogwarts is also divided into four houses, Gryffindor, Hufflepuff, Ravenclaw and Slytherin, meaning each house should have around 35 students. However the books show that Harry had only about 18 classmates, leaving fans to wonder why.

More: Jk Rowling Finds Donald Trump 'Objectionable', But Defends His Right To Freedom Of Speech

But one reader has attempted to solve the mystery with a very depressing theory. Posting on Tumblr, user marauders4evr wrote: “I just realized something. For years, we’ve all wondered how there can be 1000 students (according to J.K. Rowling) in Hogwarts when there are only a handful of students in Harry’s year.”

“The math doesn’t add up. We’ve all just assumed that it was an error. But what if there’s normally dozens of students in each house, in each year? What if Harry’s year was the exception? What if there were less students in the Hogwarts Class of 1998 because the period when the other kids would have been conceived (1979-1981) was when Voldemort’s reign of power was at its peak?”

More: Jk Rowling Apologises For Remus Lupin's Death On Battle Of Hogwarts' 18th Anniversary

“Between the dozens of adults who joined the Order, the dozens of civilians who were killed in Death Eater raids, and the dozens of adults that didn’t want to bring a child into the world, just then…It’s actually entirely possible that there was a baby drought for a few years in the wizarding world, leading to a smaller class size a decade later.”

So thanks to the actions of the evil Lord Voldemort, Harry’s year is left with less students, pretty depressing don’t you think? However the upside is, despite their small numbers, Harry’s year would be the ones to finally defeat Voldemort. Bet the Dark Lord never saw that coming.