"My goal was not to tout Mr. Bengen, but much more importantly, to encourage you Guys to try a powerful Monte Carlo simulation for planning purposes."
To that end, you cited one of the most well known papers on retirement planning as evidence of how well Monte Carlo works, even though it didn't use Monte Carlo. I pointed out that Bengen found zero real world return patterns where a 4% drawdown would fail (over 30 years); your response was to disparage the original work you cited approvingly.
It's enough to make one wonder whether you read the paper.
Instead of comparing and contrasting methodologies, you continue to effuse about Monte Carlo. Bergen took a different approach using using actual returns, that virtually everyone here can understand and use to draw their own conclusions.
In contrast, Monte Carlo spews out magic numbers (not unlike M* star ratings) that leave one to one's own devices to interpret. As guidance you proffer that you consider a
5% risk acceptable, but you didn't give any reasoning, rendering this fact useless. (I wonder why
you used these 30 year projections at all; as I recall you've indicated an age which suggests that a 30 year horizon is, shall we say, rather optimistic.)
Even the probabilities posted are meaningless because unlike Bengen, you didn't state the assumptions you used, such as the input values for mean and standard deviations of stocks, bonds, and inflation. Nor did you even apply the same asset allocation that Bengen used.
Did you consider skew and kurtosis (the
S&P 500 exhibits both)? Do you think that most people using these "push a button" tools even understand that question? (No disrespect of MFO readers is intended; many have stated that statistics is not their forte.)
The fact that a program can do thousands of computations in seconds is not so much a demonstration of the
usefulness of a program as much as it is a testament to the operation of GIGO. A scalpel is a great tool in the right hands; in other hands it can be destructive.
When all one has is a hammer, everything looks like a nail.