In this case, we use the monthly returns of the two indexes for the seven-year period between 6th May, 2009 and 5th May, 2016. The monthly return are determined by comparing the current price with the previous month’s price. The monthly returns are then used to determine the average monthly return and the monthly standard deviation.
S&P MID CAP 400 INDEX
Average monthly return = 1.2047% or 0.012047 Monthly standard deviation = 4.4024% or 0.044024 Annual return = (1 + monthly return)12 – 1 = 1.01204712 – 1 = 1.1545 - 1 = 15.45% Annualised standard deviation = Monthly standard deviation × √12 = 0.044024 × √12 = 0.044024 × 3.4641 = 0.1525 = 15.25%
NASDAQ 100 INDEX
Average monthly return = 1.4196% ...