One of the tricky things about bubbles is that they're hard to spot while you're in one. Only in hindsight, after they burst, do they become clear. One such was the dotcom bubble that occurred around the turn of the 21st century. It was a rapid rise in U.S. technology stocks, especially those in then-novel Internet-based companies, that helped lift the stock markets in general. The tech-dominated Nasdaq index quintupled in value, from under 1,000 to more than 5,000 between 1995 and 2000. Unfortunately, when many of the new, hot tech companies failed to turn a profit or perform up to expectations, investors soured on them. In 2001-02, the bubble popped. In the ensuing crash, the Nasdaq index fell over 75%. Stocks in general entered a bear market.