Another type of index is the geometric index. The calculation of a geometric index is similar to the calculation of a geometric return. The difference in the geometric index construction is the returns used are the returns for the different stocks in the index for a particular period, such as a day or year. Suppose the following three defense stocks are to be combined into a stock index in January 2016 (perhaps a portfolio manager believes these stocks are an appropriate benchmark for his or her performance): Price Shares (millions) 1/1/16 1/1/17 1/1/18 Douglas McDonnell 540 $ 103 $ 100 $ 81 Dynamics General 455 45 49 57 International Rockwell 290 74 79 81 What is the percentage rate of return on this index for the year ending December 31, 2016?