From Bespoke Investment Group:
While a 2% decline is bad enough, today's breadth is absolutely abysmal. In the S&P 500, there are currently only ten stocks trading higher and 489 trading lower (one stock is unchanged). Going back to 1990, there have been 59 other days where the S&P 500 has had a one-day breadth reading of -450 or more (as of 11:45 Eastern today's breadth is -479). On those days, the S&P 500 has seen an average decline of 3.7%, and there have only been six days where the decline was less than 2%. So as of now, the longs are getting off easy!