"Ah," said Vector, who had been too young to know this. "Okay, well, that explains that. But the war here was certainly all about blood status. And look at this." She frowned at her graphs. "In sixty-five, that's when the war started according to the history books, we had what is probably a "normal" rate of Muggle-borns - about eighteen percent - coming into Hogwarts as first-years. The graduation rate that year was normal. About six years later, there's a sharp drop in the percentage, down to more like four percent. It decreases slowly thereafter. Around sixty-nine the total population starts to fall ... so by seventy-two it's still around the same percentage but it's only one person in thirty-five first years, Lily Evans was the only Muggleborn Sorted that year."