It could well be possible to combine the gated community idea with this population drop thing. There are few possibilities to do this:<br/><br/><ul class="bbc_list"><li>It could be small community of people who were selected by what ever force before the event to form small society that was sheltered from the near extinction by some advanced means. Then it would be mostly rich and the political elite of the old </li><li>It could be community that has formed in the first, say, ten - twenty years after the disaster </li></ul><br/>In either way we could arrange things so that the society has the class / power structure of what ever kind we find appealing.