Please answer the given financial question based on the context.
Context: table of contents stock performance graph the following stock performance graph and related information shall not be deemed 201csoliciting material 201d or 201cfiled 201d with the securities and exchange commission , nor shall such information be incorporated by reference into any future filings under the securities act of 1933 or the exchange act , each as amended , except to the extent that we specifically incorporate it by reference into such filing . the following stock performance graph compares our cumulative total shareholder return on an annual basis on our common stock with the cumulative total return on the standard and poor 2019s 500 stock index and the amex airline index from december 9 , 2013 ( the first trading day of aag common stock ) through december 31 , 2014 . the comparison assumes $ 100 was invested on december 9 , 2013 in aag common stock and in each of the foregoing indices and assumes reinvestment of dividends . the stock performance shown on the graph below represents historical stock performance and is not necessarily indicative of future stock price performance. .
||12/9/2013|12/31/2013|12/31/2014|
|american airlines group inc .|$ 100|$ 103|$ 219|
|amex airline index|100|102|152|
|s&p 500|100|102|114|
.
Question: by how much did american airlines group inc . outperform the amex airline index over the 3 year period?


Answer: The answer is:0.67