A bear market is the term used when commodity prices fall and widespread pessimism creates a downward spiral of self-sustaining decline. It’s a time when high investor optimism or a 'bull market' state is replaced by fear and pessimism. Investors sell at lower prices and overall lack of confidence in the market causes the condition to take hold. One of the most famous examples of a bear market is when the Wall Street Crash of 1929 lead to the Great Depression. More recently, bear markets have occurred from March 2000 to October 2002 and from October 2007 until March 2009.