Stock Market Leaders Often Reset Their Base Counts. Here's How It Happens.

Sellers have been kept mostly at bay in the stock market since the Nasdaq composite and the S&P 500 soared on Aug. 4. That day prompted a bullish change in stock market exposure on the homepage of Investors.com. But before the Nasdaq composite gapped above its 50-day moving average in early August, it did something that leading growth stocks often…