More on time scale, this time from "Stocks for the Long Run", by Siegal.
He has stock, bond and T-bill returns from 1802-2012. He reports the following real annualised figures (I haven't included the bond figures.. they are always in between stocks and T-bills)
Over 1 year, the worst stock return he found was -38.6%, T-bills were -15.6%.
Over 2 years, the worst stock return was -31.7, T-bills -15.1
5 years, stocks worst -11.9, T-bills -8.3%
10 years, stocks worst -4.1, T-bills -5.1%.
Once you reach 20 years, stocks have always gained money, T-bills worst was still -3%.
In a sense, this is the whole story about stocks/bonds. Short term, stocks are riskier, medium-long, T-bills and bonds are riskier.