Wall Street sell-off: about $2.5 trillion lost as Nasdaq has worst crash in 18 months

1. What happened

   According to a Times of India headline, about $2.5 trillion was wiped out as the Nasdaq suffered its worst crash in 18 months. Only the headline was available, so the full article could not be checked.

2. When it started

   The date and exact timing of the drop were not available in the information provided.

3. How it spread

   The available material does not explain the mechanics of the sell-off, and specific index moves or percentage changes were not provided.

4. Why it matters

   The causes of the decline were not stated in the available material, so the reasons behind it are unknown.