Skewness characterizes
the degree of asymmetry of a distribution around its mean. Positive skewness indicates
a distribution with an asymmetric tail extending toward more positive values.
Negative skewness indicates a distribution with an asymmetric tail extending toward
more negative values.
Skewness(r1,
..., rn) = 
where r1,
..., rn is a return series, i.e., a sequence of returns for n time
periods.
