I admit that there is no type of result I enjoy encountering more than one that seems so counterintuitive, so against accepted wisdom, so surprising that I didn’t see it coming at all. Even more enjoyable is the rare occasion when that epiphany is my own. Alas, my subject today only fulfills the first criterion, as sadly, this particular insight wasn’t mine…
The related topics of, “How much active management is necessary?” (and, conversely, “How much indexing would start to be a problem for market efficiency in both pricing accuracy and liquidity?”) and the more speculative, “What would happen if everyone indexed?” are perennials that have fascinated me and many others for many years. But all such discussion always runs into the problem of Bill Sharpe. Well, not Bill in general, but specifically his observation that, properly defined (no easy task itself since this involves proper definition of the all-encompassing capitalization weighted investable market portfolio), all active management must net to zero (before fees and trading costs; and thus lower than passive returns after these subtractions).
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