No better than an excel spreadsheet. I don’t see the Monte Carlo simulation anywhere in here?
Why would you expect to see a MC simulation?
There are only three basic scenarios; taxable, ROTH, & std. 401k.
The rate of return is constant, and available to all scenarios, and adjusting its value uniformly would not affect the tax outcomes.
Adjusting the input tax rates would not affect the relationship between the taxable and ROTH scenarios, since they are the same, and since the ROTH is tax free on earnings and distributions, it will ALWAYS be better than using a taxable account.
Logically, this leaves the uncertainty between the ROTH and the std. 401k (two remaining scenarios). Since we know that there is parity between the two, if using the same input and output tax rates, what value is added by simulating various tax rates?
Now if we we’re comparing multiple variables in each scenario (e.g. differing rates of return for each – depending on available investment vehicles, the use & extent of leverage, early distributions and penalties, changes in tax laws, etc.), then running a MC simulation may be of benefit.
