The Nasdaq Composite lost nearly 80% from its 2000 peak to its 2002 low during the dot-com crash.
The index reached an intraday high of 5,132.52 on March 10, 2000. It then declined for roughly two and a half years, reaching a low of 1,108.49 on October 9, 2002. The fall was approximately 78% from peak to trough.
The Nasdaq was especially exposed because it contained many technology, internet, and telecommunications companies. Investors had bid up shares on expectations of rapid online growth, sometimes despite minimal revenue or no profits. When confidence reversed, venture funding dried up and many companies failed or were acquired.
The crash did not mean that every technology company disappeared. Firms with durable businesses eventually helped drive a later technology-led recovery, but the index did not regain its 2000 closing high until 2015.