[["as of december 31,", "2012", "2013", "2014", "2015", "2016", "2017"], ["arconic inc .", "$ 100", "$ 124.15", "$ 186.02", "$ 117.48", "$ 99.40", "$ 147.47"], ["s&p 500 aeindex", "100", "132.39", "150.51", "152.59", "170.84", "208.14"], ["s&p 500 aematerials index", "100", "125.60", "134.28", "123.03", "143.56", "177.79"]]