Jason, thanks for your response. I used the equity benchmark index for Indian equity markets. Yes, I did use daily mean and standard deviation. The numbers I got are different from S&P500, obviously, but they are not too different I guess. My question is largely to do with the basic construct of normal deviation. I calculated the number of times, the returns fell into the range of +1 and -1 standard deviation. I was interested in seeing this on a yearly basis. Yes, most of the times the distribution was leptokurtic. The +1 and -1 SD occurences range between 75 - 85% ( I am rounding of quite a bit here for simplicity). What I am happy about is that almost all the times the distributions can pass for a normal distribution. Did the chances of getting normal distribution improve because I used 'standard deviation' ? After all isn't standard deviation computed from mean - sum of squared.... If I used anything else to measure risk, other than standard deviation, would I still get such near perfect central tendencies?