U.S. stocks fell on Friday, with the S&P 500 returning to negative territory for the year as losses accelerated in midday trading. The benchmark index lost 0.8%, and is now down less than 0.1% for 2018 thus far. While the S&P has been negative for the year multiple times in 2018, it had recently returned to the green. It has traded in positive territory for the year for the past four sessions. The Dow Jones Industrial Average fell 0.8% on Friday, bringing its year-to-date move to a drop of 1%. The Nasdaq Composite Index fell 1.1% on Friday, but remains up 3.7% for the year. The day's losses were widespread, pressured by weakness in the energy sector and by a sharp decline in Apple Inc.