U.S. stocks slid on the final trading day of the year, making a negative end to 2015 highly likely. The S&P 500 had started the session a fraction higher for the year. The tech-heavy Nasdaq looks in better shape, likely to close out with gains of more than 6 percent. Apple (AAPL) shares tumbled more than 1 percent on Thursday, the biggest drag on the Dow. The world's largest company is down just over 4 percent for the year so far. Economic activity in the Chicago area fell at its fastest pace in December since 2009, according to the latest Chicago PMI numbers. Activity in the Midwest has spent much of the year in contraction. Chimerix (CMRX) climbed after billionaire Steven Cohen's investment firm disclosed a 5.3 percent stake. Shares tanked earlier this week after the biotech company said its antiviral drug had failed to reduce infection in stem-cell transplant patients.