Google tells me that there are almost 2900 billionaires in the world (nearly 800 in US alone). Considering that the volcano explosion and tsunami came quicker than they thought it would, I doubt all the billionaires would have made it to Colorado especially when the other countries started dropping bombs. The population has small amount of billionaires with their families and people that they brought, government people and their families, and the rest would be the people who will need to run and operate all parts of that city.