The Value of Sound Financial Decisions: From Alpha to Gamma
David Blanchett and Paul Kaplan at Morningstar created a similar study about the value of good decision making. Their results and approach are different from those of Vanguard , but the goal is the same: to quantify the costs of poor and good decision making.
Pfau, Wade D. PhD, "The Value of Sound Financial Decisions: From Alpha to Gamma" (2016). Faculty Publications. 485.