The Safe Withdrawal Rate

The 4% safe withdrawal rate is based on William Bengen's study into past market returns and risk. With a 96% certainty you could withdraw 4% from your portfolio every year and adjust it upward for an inflation, the money will never run out during a 30 year retirement. The idea of working backwards to get to a life where you're doing mostly things you want to do was able to change my mind about when I should retire.