What qualifies as a 90% down day (NPDD)?

A 90% down day, also referred to as a New York Stock Exchange (NYSE) "90% down day" or NPDD (New York Stock Exchange Down Day), is characterized by significant selling pressure in the market. The correct definition states that both downside volume and downside points must exceed total volume and total points by 90%. This means that for the day, a remarkable proportion of trades were in stocks declining in price, indicating strong bearish sentiment among investors.

When this situation occurs, it suggests that the market is experiencing a considerable downturn, as the volume of selling is far greater than buying, combined with a substantial decrease in the overall market points. Therefore, the definition captures both the breadth of the market decline (measured by volume) and the depth of the decline (measured by points), highlighting an overwhelming negative sentiment.

The other options do not encapsulate both necessary criteria that define a 90% down day, which is why they are not correct. For example, just having downside volume exceed upside volume by 90% does not account for the significance of the decline in points or the total market context. Similarly, a condition where all stocks close lower for the day is an extreme scenario that does not specifically quantify the relationship between