The most common cause of low prices is pessimism - some times pervasive, some times specific to a company or industry. We want to do business in such an environment, not because we like pessimism but because we like the prices it produces. It's optimism that is the enemy of the rational buyer.
Warren BuffettDiversification is a protection against ignorance. It makes very little sense for those who know what they're doing.
Warren Buffett