It's Who You Know, and How Many

This is not new, but worth repeating:

When Aldrich visited villages in India hit by the giant 2004 tsunami, he found that villagers who fared best after the disaster weren't those with the most money, or the most power. They were people who knew lots of other people — the most socially connected individuals. In other words, if you want to predict who will do well after a disaster, you look for faces that keep showing up at all the weddings and funerals.
"Those individuals who had been more involved in local festivals, funerals and weddings, those were individuals who were tied into the community, they knew who to go to, they knew how to find someone who could help them get aid," Aldrich says.

 Conversely, some years back there was a heat wave in Chicago which killed a lot of people.  A sociologist studied the deaths and found the people were those who had lost all ties to the community, particularly the old who no longer got out.