Don't report me to police, but I think about this all the time. Not because of evolutionary purposes, but I keep thinking that this earth is too damn crowded.

My main criteria was that if suddenly half the population disappears, the resulting chaos should be minimal. After trying out multiple possibilities, I've come down to this: Each family should be done into the half. In ideal scenario, in family of 4, one of the parents will go and one of the child will go. In the most cases, earning member of the family will have higher odds of surviving. Also, the distribution of male, female should be maintained so that two surviving family can come together, if they wish.