If something like an Asteroid was known to be on a collision course, would those in power inform the citizens of the world and cause a big panic?
It's hard to say. When the Chernobyl power plant melted down that information was kept away from the public for awhile until they couldn't suppress it any longer. This caused preventable deaths.
Governments have a tendency to control information for strategic benefit, and would weigh the pros and cons of releasing it.
It's the same sort of reasoning for economic crisis. There would be people who know in advance. That doesn't necessarily mean they would be announcing it on CNN before hand because that would cause panic and could make it worse. It's more strategic to not tell people, profit it from it, and pretend 'nobody could have seen that coming'
