[["( dollars in millions )", "years ended december 31 , 2017", "years ended december 31 , 2016", "years ended december 31 , 2015"], ["net sales", "$ 15191.5", "$ 13981.9", "$ 12988.7"], ["gross profit", "2449.9", "2327.2", "2115.8"], ["income from operations", "866.1", "819.2", "742.0"], ["net income", "523.0", "424.4", "403.1"], ["non-gaap net income", "605.8", "569.0", "503.5"], ["adjusted ebitda", "1185.6", "1117.3", "1018.5"], ["average daily sales", "59.8", "55.0", "51.1"], ["net debt ( 1 )", "3091