With the raw data, I calculated the mean return, standard deviation, and the coefficient of variation. The results are as follows: May/October had a mean return of 1.52%, standard deviation of 8.55%, and a coefficient of variation of 5.64. November/April had a mean return of 7.30%, standard deviation of 10.08%, and a coefficient of variation of 1.38. Finally, a Buy/Hold strategy had a mean return of 0.74%, standard deviation of 4.07%, and a coefficient of 5.53.Any questions about the power of seasonality within the stock market? I didn't think so. Another way of looking at the above performance is as follows: "One dollar invested in 1950 using only November through April investment periods each year has grown to just shy of $43 today. Alternatively, one dollar invested only in the May through October periods since 1950 is today worth less than $2."
