A bull market, also known as a bull run, is one in which shares are generally rising in price. The investors are generally optimistic and keen to buy, thereby driving prices up further. A good example is the U.S. stock market in the early nineties, when all the stock market indices such as the Dow Jones rose almost continually. A bear market, on the other hand, is one where share prices are falling due to investor pessimism. The most famous bear market was the Wall Street Crash that started in October 1929.