The wealth management industry has consistently cited the “70% failure rate of wealth transitions” put forth by Roy Williams and Vic Preisser since the 1990s. In this detailed International Family Offices Journal article, each citation for this assertion is tracked back to original sources, finding the “rule” was built on a single limited study from the 1980s that was superseded by better research decades later. The article also critically reviews Williams and Preisser’s own research on the supposed causes of these family failures. Recommendations are outlined for developing better research about family wealth longevity in the modern era.