David Henderson's "A Nobel for the Random Walk of Stock Prices" (op-ed, Oct. 15) describes me as "one high-profile beneficiary of Mr. Fama's insight," allegedly inspiring my founding of the Vanguard 500 Index Fund in 1975.

This is untrue. Perhaps to my shame, I didn't even learn of Eugene Fama's "efficient market hypothesis" (EMH) until a decade after my creation of the 500 Index Fund. Rather, I was inspired by another Nobel laureate, economist Paul Samuelson, who in his 1974 essay in the Journal...