All of the S&P 500's 11 sectors were trading in negative territory around midday Friday, led by sharp declines in information technology and materials. The tech sector /zigman2/quotes/207444675/composite XLK -0.35% was off 1.5%, while materials were down nearly 2%, which was weighing on the broader index. Health care was the best performing among the 11 sectors, but struggling to stay in positive territory. The S&P 500 index /zigman2/quotes/210599714/realtime SPX -0.11% was down 38 points, or 0.9%, at 4,434, struggling to stay above its 50-day moving average at 4,436,67, according to FactSet. Meanwhile, the Dow Jones Industrial Average /zigman2/quotes/210598065/realtime DJIA +0.21% was down 0.6% at 34,531, while the Nasdaq Composite Index /zigman2/quotes/210598365/realtime COMP -0.82% was down 1.2%. All three benchmarks had erased earlier weekly gains.