Probably a very simple question but here goes.
I am looking to calculate the Sharpe ratio for some funds in excel (173 funds to be exact). The monthly returns I have are from January 2006 to December 2015 inclusive. This 10-year period is the period of interest in my dissertation that I am currently completing. I have found the excess returns (returns - riskfree rate) for every month of every fund. I then found the average of the excess returns over the 10-year period for each fund, then divided by the standard deviation of the returns over the 10-year period for each fund.
All 173 funds display a positive Sharpe ratio, however, which seems inaccurate. Have I done something wrong here?