Portfolio standard deviation in the detailed data window
Posted: Mon Nov 20, 2017 10:01 pm
How accurate is the sd listed in the detailed window? It would be incredibly helpful if it were based on the actual investment data (mean, sd, of each investment plus covariance between each investment.) Obviously that don't happening. So I assume there's an implicit assumption here that the three asset types (taxable, tax deferred, tax free) are independent and uncorrelated, so the variances add. If so, the sd value is wrong unless sd statistic is very robust or the correlations are close to zero.
So how is that standard deviation value calculated and how is it used?
So how is that standard deviation value calculated and how is it used?