Returning to the conundrum of what is the best portfolio mix when you consider multiple different diversifying assets, I used the PortfolioCharts WithDrawal Rates page (
https://portfoliocharts.com/charts/withdrawal-rates/#chart) tested combinations of 4 assets:
US LCB
Gold
REITs
10y bonds
Theoretically working in 5% allocation step increments, 2 different assets gives us 21 different combinations, 3 assets gives us 231 possible combinations and 4 assets gives us a total of... 1771 possible combinations. That's a lof of combinations to test!
Fortunately we don't need to test every one of these , as we already know what the best combination with just 2 assets, (65/35 stocks gold) we can take the equity allocation of that as our base scenario and introduce a 3ed asset, find the best combination for 3 assets, then use that as a base case to test the effects of the 4th asset...
In short, here's what I came up with..

Key takeaways
- If considering just 2 assets (stocks & gold) the best combination is 65/35, which supports a SWR of 5.7%. No other asset by itself will diversify a stock portfolio as well as gold. (from opening post).
- Adding in the next best asset (REITS) is very worthwhile. While REITS by themselves don't diversify as well as gold, a combination of REIT+Gold is hugely beneficial to the portfolio, and in fact the optimal portfolio composed of these 3 assets will hold more REITS than gold in a 45/25/30 stock/gold/REIT mix.
- the SWR continues to improve as you reduce equity expose from 65% (and by inference from 100%) and allocate it amongst diversifiing assets. This is true until we get all the way down to a 45% equity allocation, at which point the starts to go the other way again, so 45% is the optimum equity allocation when considering 3 or more assets.
- Taking our 45/25/30 best 3-asset portfolio and modifying it with an allocation to 10yr bonds
fails to improve portfolio. With a small 5% allocation (taken from stocks or REITs) the SWR remains at 6.4% but the perpetual withdrawal rate (PWR - which I look at as a sort of tie-breaker) falls by 0.1-0.2%. A 10% allocation sees a more deleterious reduction on the SWR. The reduction in portfolio efficiency is more pronounced if you take it from the gold allocation than from the REIT or Stock allocation.
Baseline 100% US LCB: 3.8% SWR
Best Stock/Gold combination: 65/35, 5.7% SWR
Best Stock/REIT combination: 40/60, 5.1% SWR
Best Stock/Gold/REIT combination: 45/25/30, 6.4% SWR
Best Stock/Gold/REIT/10YUST combination: 45/25/30/0, 6.4% SWR
Personally, these findings were revealing to me, not for the reaffirmation that it's difficult to make a case for bonds on the testing numbers presented here, but how well the combination of REITS
and Gold works (considerably better than either by themselves). I do hold some REITs already.. and will definitely be increasing my exposure to them going forward.