Here is a chart of the index value for the S\&P 500 and the United Kingdom's main equity index, the FTSE 100, from the end of 2008 to early 2015 . The labels have been removed. One index has clearly outperformed the other. Over this period, there was a technology boom and an oil crash. Here are pie charts showing the early 2015 index compositions by industry for both the S\&P 500 and the FTSE 100. Which index outperformed