Which U.S. index lost about 78% during the dot-com crash?

The Nasdaq Composite lost about 78% during the dot-com crash.

The index reached 5,048.62 on March 10, 2000, at the height of the dot-com bubble. It fell to roughly 1,114 in October 2002, a decline of about 78% from the peak.

The Nasdaq Composite includes thousands of common stocks listed on the Nasdaq stock market and has a strong technology-company representation. That technology concentration made it particularly sensitive to the collapse in internet and communications valuations.

The Nasdaq Composite is often confused with the Nasdaq-100. The Composite covers nearly all eligible Nasdaq-listed common stocks, while the Nasdaq-100 tracks 100 of the largest non-financial companies listed on Nasdaq.