I?ve also wondered if just increasing from 50-50(what the 4% rule is based on) to 75-25 is enough to give a 100% chance of success at 4%? Also social security included? Then adding any additional income and spending flexibility, maybe it?s overkill? I know inflation is a major concern. Your last sentence made me think about year 0, a big negative return then could really have an impact.
Thanks again! Awesome response!
This can all be modeled in cFIREsim. Try it
http://www.cfiresim.com/100% stock has greater volatility than 75/25 or 50/50. Volatility combined with a poor sequence of returns can mean worse results. In the original Trinity Study data, 100/0 and 50/50 have worse results than 75/25. (See Table 2 in this post:
https://www.gocurrycracker.com/what-is-your-retirement-number-the-4-rule/)
The 4% rule is not based on 50-50. It is based on a wide spectrum of portfolio allocations.
There is no right answer to the question of how much you can increase spending, but the answer is similar to the early retirement question: how much do I need to save?
The only additional risk factor in continually stepping up spending is that at some point you will reach a peak in the market followed by some poor market return years. That peak might be a case where the 4% rule fails going forward. But then again it might not.
The question to ask yourself: will this incident be worse than the worst time to retire in history? And if so, what am I willing to change in regard to spending or earning to compensate (Worst time to retire example:
https://www.gocurrycracker.com/the-worst-retirement-ever/)
(Note that the worst case retirement wasn't at a market peak - the market plunge didn't happen until 10 years in)
Or, another way to look at it:
https://www.gocurrycracker.com/the-go-curry-cracker-endowment-fund/