A math-minded 4chan commenter has done a bit of number-crunching to arrive at an interesting theory: that The Walking Dead's zombie plague should've ended after a year, simply by biter attrition.
While the passage of time is difficult to discern in either the comic or the TV series, it would appear to be about two years since the outbreak began in the former, and a little less in the latter -- more than enough time to dispatch the flesh-eating hordes. In theory, anyway.
BuzzFeed adds visual aids to the equation, which makes some necessary, maybe even generous, assumptions but seems pretty sound on the surface (math was my worst subject, so you may not want to take my word for it, though). In short, even if we assume that 99 percent of the population of the United States (300 million people) was infected, that would leave about 3 million survivors. If they formed groups about the size of Rick's -- say, 20 or so people each -- and each person in a group killed 10 walkers a month, they would've run through about 360 million zombies in a year.
Of course, some of those assumptions are probably a little off, as not all of the initial survivors would join groups larger than, say, their immediate families, and the children, the elderly and the infirm might never kill a zombie. But even if you shave off several million of the walking dead, the number still exceeds 300 million.
Reddit users dig even deeper, suggesting that 99.9 percent of the population might be infected, leaving just 10,000 initial survivors in the United States -- thereby blowing the theory entirely.