Suppose we have the following Treasury bill returns and inflation rates over an eight-year period:

Year	Treasury Bills	Inflation
1	7.70%	9.20%
2	8.46	12.88
3	6.31	7.41
4	5.48	5.24
5	5.89	7.17
6	8.11	9.52
7	11.10	13.84
8	12.70	13.19

What is the average real return for Treasury bills over this period? (A negative answer should be indicated by a minus sign. Do not round intermediate calculations and enter your answer as a percent rounded to 2 decimal places, e.g., 32.16.)