I have been following RE for at least 10 years as I have been working my way to that goal. I have a DORY excel model from 1998, that I have taken apart and put back together with some changes.
I wanted to explore a highly variable withdraw rate. First, I added the last 9 years of financial data to the model from DORY, but for simplicity sake, I dropped all Fixed Income and focused on a 100% SP500 portfolio.
Next, I added the following rules:
I can configure the withdraw rate based on the Market Return - Inflation (the real return) to take a minimum withdraw in bad years and a large withdraw in good.
Second, I have configurations so the withdraw rate will vary through retirement - start low the first couple of years to adjust to retirement, middle very high, end moderately low - or any other strategy one wants to explore.
Third, I added a configurable rule that forces a minimum withdraw even in a good market if the portfolio value is a specific percent (inflation adjusted) below where it started. This really helped prevent failures in 1929, 1966, etc.
Forth, if the portfolio gets more than a specified percent (again inflation adjusted) above the starting portfolio value (maybe 50%), the withdraw rate is increased by 3% (or whatever value you want it to be).
I'm still working on this model and convincing myself it is accurate, but the initial results are very interesting.
For a 40 year cycle, 100% survivable, the worst starting year 1902, had an average withdraw rate of 3.65%. Only 3 cycles were below 4.0% average withdraw rate. But the average year was 6.3% and the best year was 8.5%.
Has anyone else experimented with highly variable FIREcalc?