https://retireearlyhomepage.com/Bengen_4.2_percent.html

"Bengen has finally realized that 50 or 60-year pay out period returns for the S&P 500 converge to a narrow band (i.e., asymptopic). Though I would quibble with the 4.2% figure. While we can calculate historical "safe" withdrawal rates to 3 or 4 decimal places, I don't believe you can predict the future with more than one significant digit of accuracy. Thus, I'd say the safe withdrawal rate (SWR) is closer to 4% than 3 or 5. Of course, the SWR for pay out periods of less than 30 years should rise above 4%."