"Near the top of the market, investors are extraordinarily optimistic because they've seen mostly higher prices for a year or two. The sell-offs witnessed during that span were usually brief. Even when they were severe, the market bounced back quickly and always rose to loftier levels. At the top, optimism is king, speculation is running wild, stocks carry high price/earnings ratios, and liquidity has evaporated. A small rise in interest rates can easily be the catalyst for triggering a bear market at that point."