While the S&P 500 may be ending 2016 with double-digits gains, almost a third of the index' individual stocks have gone down. Here are some of the perpetrators you should dump from your portfolio. Abbott Labs (ABT) shares have lost about 15% of their market value, which means that they're under-performing the S&P 500 by about 25%. Shake Shack (SHAK) rose 10% on good third-quarter results but the stock has been forming a bearish reversal pattern. Enstar Group's (ESGR) chart is starting to look "toppy" and you should sell it as soon as it hits $190. Alexion Pharmaceuticals (ALXN) has been shedding more than 35% of its market value since January and could go down even more. Bank of New York Mellon (BNY) has rallied 15% since the beginning of the year. The sell signal trigger will happen when it hits $47 a share.