The S&P 500 plunged 3.3 percent between Friday, January 22, and Friday, January 29. It was the biggest weekly decline since October, with 85 percent of the index’s members losing value. The selloff also dragged stocks into negative territory on a year-to-date basis.
Apple (AAPL), which didn’t even make the Top 10 in June or July, was the busiest stock at TradeStation last month. The surge in activity came after a transformative earnings report drove the smart-phone giant into new record territory.