Most of the rough sledding in the U.S. stock market this year has been attributed to the negative effects of "lower for longer" oil prices and the slowing of the Chinese economy.
Those are undeniably negative catalysts, but there's another simple catalyst at play that doesn't get quite as much attention: Shares of Apple, the largest company by market value, have been punched in the gut in the past year. Apple's stock has plunged 25 percent since its last record closing price on Feb. 23, erasing almost a quarter-trillion dollars in market value.
When looking for individual stocks to blame for either this year's plunge or the longer-term retreat in the S&P 500 since its peak on May 21, Apple stands out decisively. The stock has shaved 20.4 points off the index since its May record, almost four times the next biggest contributor, Exxon Mobil.