Very nice, Tyler.
For your 60/40 stocks/gold example I assume you are leaving out capital gains taxes. What would you get if you included a 15% tax rate in your annual rebalance?
I wish it were that simple! ;)
That's a very good question, and one I do not have an immediate answer for. Yes, all calculations ignore taxes.
Aside from the overhaul the spreadsheets would require (I tried, but it's not a quick change), there are practical reasons why it's difficult to generalize.
1) The data I have is for total returns only, and I cannot separate dividends and interest from capital gains.
2) Accounting for cost basis in the calculations is non-trivial.
3) Gold is taxed differently than stocks and bonds, and varies even more by how it's held.
4) Tax-loss harvesting and other tax-mitigating strategies will change the results.
5) Throw in state taxes, tax brackets, deductions, and 44 years of ever-changing tax law and it gets... complicated.
So the calculations all apply for tax-deferred accounts, but in a taxable account YMMV. Every investor needs to look at how their specific tax situation may impact their portfolio choice and plan accordingly. Some portfolios may work better than others for different people.
BTW, your question reminds me that I forgot to add the tax disclaimer to the new assets page. Thanks!