I agree with Urban. Without a population decrease, I'm thinking along the same vein as Urban whereas the<em>havenots</em>would severely outnumber the<em>haves</em>and could easily overpower them with just sheer numbers... ulness they were killed which would lead us back to a population decrease, just on a different scale. The decrease doesn't have to be as sever as 99%, even though this would still leave 68 million people on earth and nearly 3.5 million in the US. Granted this is much, much less than the nearly 7 billion total earth population and 307 plus million in the US, but it's still quite a few folks... they just have a whole shit-ton more room to do whatever and resources help them survive or achieve other ends.<br/><br/>I also agree that the best explanation for a massive population decrease would be a pandemic of sorts such as some monster flu virus (avian or swine or mabye another flu... the flying pig flu. Hey, that could be kinda funny and neat with everyone referring to the event with some sort of "when pigs fly" reference. HAHA! :) ) On the other hand, if we wanted it to be more mysterious and add some sci-fi type flavor to the story for our more sci-fi nerdy geeky types ;) we could have some unexplained event such I mentioned earlier where everyone simply vanished off the face of the earth in the blink of an eye. I would still steer clear of aliens and religion, though, and perhaps use something more along the lines of what DA and Haibane mentioned earlier with time dialation or some unexplained comsic rift that transported most everyone somewhere or sometime else and we are the ones left behind? Food for thought.<br/><br/>Having only 1% of earth's population, just as a sidenote, would take us back to the population of earth as it was sometime between 1,000 B.C and probably 500 B.C.<br/><br/>