I think you missed the point(s). First, there were two guardrails strategies tested, a very simple Guyton-Klinger and a very complex probability-based version. Now look at Exhibit 15. They both performed about the same, albeit both with relatively high standard deviations. What this tells you is that there is little benefit to adopting a very complicated guardrails strategy when a simpler one will do. (But financial advisors like to plug the more complicated ones to give you something to pay for – listen to that happening on the Sep 17 White Coat Investor podcast for an example. This is the latest, greatest marketing schtick many have landed on.)
But also look at the base withdrawal rates in Exhibit 15. Despite their complexities and high variability, neither of the guardrails strategies really performed significantly better than the dirt-simple "Actual Spending" strategy in terms of starting withdrawals. They all added just over 1% to the standard SWR.
The "Actual Spending" strategy is based on the observation that real retirees do not experience inflation at the CPI rate, but 1-2% less than that. So all you need to do to see if you qualify and implement that is monitor your own spending to see how it increases over time. You are probably doing that anyway.
Our retirement experience is that our lifestyle costs have actually been declining, not going up, and the only exceptions are discretionary items like renovations and big vacations.
But if you were to combine "Actual Spending" with a simple Guyton-Klinger, you can have the best of both worlds. No complex calculations will be necessary. (This is similar to what most people actually do in real life anyway.)
Don't confuse complexity with efficacy. "More calculating" with fancy formulas does not yield better results here. There is more than one way to skin the variable withdrawal strategy cat, so don't limit yourself to only one idea.
