Friday the 13th turned out to be bad luck for the stock market as stocks ended with ugly losses, weighed down by another big drop in oil and weak retail sales data. The Nasdaq lost 1.5%, the Dow Jones industrial average fell 1.2% and the S&P 500 gave up 1.1%. Small caps were relatively unscathed as the Russell 2000 eased 0.6%. Preliminary data showed volume on the NYSE and Nasdaq coming in higher than Thursday’s levels.