Thirty years ago, William Bengen’s Determining Withdrawal Rates Using Historical Data was published in the Journal of Financial Planning. The uninspiring title did little to dampen interest in his research. Using return histories for stocks, bonds and cash back to 1926, Bengen proposed appropriate withdrawal rates on retirement savings. These were based on the simple principles that past returns in capital markets are a reasonable guide for the future, that savers aim to maintain their standard of living through their retirement years, and that no one wants to outlive their nest egg. He made adjustments to accommodate inflation and for those wanting to leave bequests, but the moving parts of his analysis were few. Nevertheless, that research has been foundational in the field of retirement planning ever since.